World Tennis Number (WTN) algorithm changes coming

I saw a mention of an email sent out from World Tennis Number about algorithm changes, but I hadn't seen it, so I went and visited their site and in the news section is a story on World Tennis Number Algorithm Enhancements 2026.

Many of you probably don't follow your WTN, as for USTA League players it is largely meaningless other than it being a rating you can track.  But it doesn't directly relate to your NTRP rating or dynamic rating, nor is it used for anything related to leagues.  I'm a ratings geek so I do follow mine, and if you follow yours too I'd be interested in hearing from you or leaving a comment about your experience with it.

If you have followed along with WTN news, you will be aware that this isn't the first time there have been changes.  At a minimum there were changes in 2024 to try to have WTN ratings represent a player's ability more quickly, and widespread adjustments in 2023 to redistribute players along the 40:1 scale.  You can see all my WTN posts here.

So, this isn't the first change, what is changing now?  A quote from the article is the changes will "improve rating accuracy, reflect real match performance, and support player development at all levels of the game".  Here are some highlights from the news article above:

• Changes go into effect for the calculations on August 12th
• There will be a rolling 3-year rating window where older results gradually drop out of the calculations
• The algorithm will use game-level scores, not just who won the set
• Ratings may be "gently adjusted" based on age, time since last match, and "typical development patterns"

The biggest news to me is the move from only looking at who won a set to factoring in the score of the set.

Up to this point, if you won 7-6,7-6 the WTN algorithm would treat that the same as if you won 6-0,6-0.  In my opinion, there were pros and cons to this.

On one hand, winning sets, and the match, is what matters, how you do it doesn't really matter, so if someone had a track record of winning close matches, they should be rewarded for that.  The algorithm was also a little simpler and easier to understand (or reverse engineer?) and less prone to being gamed by someone managing scores.  If someone played enough and against stronger and weaker players and accumulated wins and losses, their rating would settle it and represent their level.

On the other hand, ignoring the score is ignoring valuable data.  Clearly, winning 6-0 is different than 7-6 and ignoring that seems foolhardy.  If someone plays a strong opponent and keeps it close, they don't get rewarded for that, and if that player happened to always play strong players and lose, their rating could perhaps inappropriately keep getting worse.  Using the score in a set would allow for rewarding a player for keeping it close.  And if someone didn't play a lot of matches, their rating could inappropriately go up or down based on very few matches with limited data, and using the game score would fill in some gaps.

Now, in the algorithm to date, winning sets in a given match was not treated equally, but how much it helped your rating depended on your rating and the rating of your opponent.  Win a set against a much weaker opponent and your rating would improve very little.  Win a set against a stronger opponent and that would raise your rating a lot.  So some of the cons were mitigated a bit and there would be some limit on what a player's rating could get to by only ever playing weaker players and winning.

So, is this change a good thing?  I think so, but it will depend on exactly how it is implemented.  I don't know of anyone trying to game their WTN, but using game scores opens the door to that.  But if that is a rare occurrence, WTN ratings may become a little more representative of a player's ability.

What do you think?

The World Tennis Number (WTN) changed again

Being someone very interested in ratings, I've followed the World Tennis Number (WTN) as an interested party, including doing some early analysis on how it mapped to NTRP.  You can see all my posts on WTN here.

The ratings themselves have gone through a few "adjustments", most recently just over a year ago, but a notice was sent out of another impending adjustment a few days ago, and it appears with today's update, it has gone into effect.

Both the USTA and LTA sent e-mails with a heads up about the change, from the LTA's e-mail, the goal was to:

• Improve accuracy by adjusting where some players start on the scale
• Make every match count whilst recognizing the difference in ability between you and your opponent
• Faster movement of a player's WTN to reflect their level

The USTA's e-mail said more.  On where players start:

Based on the data, it’s become increasingly apparent that some players are being initialized too high. We want junior players to experience appropriate improvements to their rating as their game improves. This change will ensure players see this reflected in their rating as their level improves.

Regarding faster movement:

Player ratings will transition to their ‘true’ skill level faster from the initial rating given to them. This will mean that when a player is given an initial rating that is too low or too high, they will update to a more accurate rating much faster from their first few matches.

And about matches counting:

Every match counts towards a player's rating but it’s important that the rating change reflects the difference in ability. Players will experience smaller changes to their WTN in matches when losing to a superior player. However, players will still see a sharp increase to their rating should they beat a player with a substantially better rating.

The USTA does have a document highlighting the changes with an FAQ as well.

This all seems good, but we'll see how it plays out.

On a personal level, the adjustment a year ago saw my rating get worse, going from around 21 one all the way up to 29 (remember, the scale is from 40 to 1, 40 being the lowest/worst rating).  That was a pretty major shift, seemingly because the USTA felt as a group, adult league players were rated way too high.

This time around the shift went back the other way, but was far smaller, I went from a 27 to 25.

Is this better?  I'm not sure, it is difficult to do a thorough analysis on WTN as the data isn't readily available.  My rating getting better feels nice, but it is just a number, and one league players as a whole don't really seem to follow closely.

What do you think?  Do you care about your WTN?  Do you check it each Wednesday when the new ratings are published?

USTA introduces new player summary dashboard

The USTA sent out an e-mail earlier today to presumably all USTA members, announcing a new player summary dashboard players will see when they login to usta.com.

Specifically, when you are logged in, there is supposed to be a summary that shows your NTRP level and your WTN, both singles and doubles.  This is great, except ...

The example they included in the e-mail, at least the one I received, is a bit nonsensical.  It lists the following information on the dashboard:

• NTRP Rating: 2.5S
• Self Rated Skill Level: Advanced
• Singles WTN: 17.9
• Doubles WTN: 16.5

So we have someone that self-rated at the lowest level available but is "Advanced"?  And has WTN ratings that you might find NTRP 5.0s having?  Yes, it is just a screenshot/image in an e-mail, but you'd think the USTA could have created one that isn't a set of contradictions.

Moving on, when you login and go to the Home page, there is no sign of the player summary dashboard.  You see a huge image with the text "National Tennis Players" that takes up a good half to two-thirds of the screen depending on your resolution and how big you have your browser window, and scrolling down a half page or more still reveals nothing about the player summary dashboard.

There is a link on the right near the top of the page to navigate to "My Profile" and doing so does get to a page that has some profile information, but at least on my browser on a laptop, I don't see the player summary dashboard.  Here though i can scroll down a page and see my NTRP level and both WTN ratings, but it is laid out differently than the example in the e-mail.  So where is this new player summary dashboard?

It turns out that back on the Home page, if you scroll down a page and a half or more, you finally get to the summary like was in the e-mail.  It is a reasonably nice layout of the pertinent information all in one place so that is nice, but it would be nice if one didn't have to do so much scrolling or navigating to get to it.  UTR for example has your rating right at the very top of the page, and on the profile page even begins to show some recent matches without having to scroll.

So the summary is nice, but it would be better if it was more prominently displayed or easier to get to.

Another observation is that I have been a C rated player for years, but the summary has a spot for a self-rated skill level that I can select.  I'm not sure what the meaning of that would be, but it is there.

There is another button on the summary to "Scout" players.  It sounds like something useful, but does nothing but take you to the existing page to search for a player.  Note that this search is more useful than the one on the WTN site.

On the profile is big "World Tennis Number" text that is a link to the WTN site, but that is all it goes to, the generic site.  If you navigate to another player's profile, then there is a link to view their WTN profile and it goes directly to them, but that doesn't show up for me on my profile which is odd.

Regarding the WTN site, their search is terrible.  Trying to search for friends and teammates by name often doesn't bring them up, but brings up other players with a matching first name but a different last name than I searched for.  And when you find a player to have to ensure animations to show the WTN to see the number.  It is all very awkward and the USTA site is actually better for this for the most part.

What do you think of the new summary?  Do you even care about tracking your WTN?  Do you find either of the USTA or WTN sites useful to go scout players?

A bit more on the recent WTN algorithm change / adjustment

I wrote a few days ago about the recent significant change to WTN ratings that the USTA sent a notice out about, and many players saw their WTN get larger (worse) overnight, some in the high single digits, but others went up 10 or more.

I don't have any detailed analysis yet, but do have a few more observations.

The USTA published an FAQ about the changes that is worth a quick read, but it had a few interesting explanations.

First, some insight into why the change was made:

These enhancements to the ITF WTN algorithm will reposition cohorts of players on the current scale of 40-1 and ensure that players from all over the world are more accurately aligned, particularly with regard to different age groups. While ratings are likely to be adjusted, players will likely see movement relative to their age group.

So, they seem to have concluded that different age groups of players were rated correctly relative to each other.

Going on, they get more specific:

Adult players aged between 19-29 should expect only minor changes to their ITF World Tennis Number. Larger changes begin to occur for players over 30 years old that regularly play against players of a similar age. Adult players over 30 will see their numbers move down the scale (towards 40), this is to create some balance with Junior players and to ensure full use of the 1-40 scale.

This is consistent with my anecdotal observations that USTA League players around me, for the most part age 30+, have seen their WTN get larger and closer to 40.  I haven't looked at any juniors, but believe their statement to be true.

And from what I see, USTA League players are by and large are all in the mid-20s and higher.  I see 4.5 and 4.0 men in the mid-20s and the majority of league players are at 3.0-4.0, so that means the majority of league players are being squeezed into the 25-40 range.  That is quite a bit less granularity than we had before (15-40) so we will see how that works out.

Regarding juniors, the FAQ states:

Junior players aged 10 and under will most likely experience a movement down the scale, (towards 40) with players who are aged 17 and 18 moving up the scale (towards 1). The player ratings are now more of an accurate reflection of age, with a general incremental increase expected from aged 10 upwards.

I've also heard from players in the UK and US looking at comparisons with players in Europe that prior to this change, there seemed to be a disconnect in that what appeared to be similarly skilled players from Europe and the US had significantly different WTN ratings, those in the US having lower numbers, so this adjustment seems to have addressed that, at least somewhat.

All of this highlights the challenge of a single algorithm that tries to put all tennis players in the world on the same scale.  Whether it is age groups or countries or other geographic grouping, you will inevitably have islands, or cohorts as the FAQ says, that all play each other, but have little to no play with other islands or cohorts.  When this happens, the algorithm has very little data to go on to reasonably ensure players from those different groups are appropriately rated relative to each other.

This is probably the biggest challenge for the WTN, and as such one would have hoped a lot of effort would have gone into reviewing this and getting it right prior to launch.  If adult USTA League players were rated in the teens and similar recreational players from Europe were in the 20s, that should have been one of the first things that was reviewed and stuck out.  Similarly if all juniors regardless of age were clumped together, or juniors relative to adults seemed off, this could have been observed far earlier and address before WTN was launched.

There are ways an algorithm can address this, notably by looking at the matches that are played between the islands of players, and giving them more weight in determining the relative ratings for the group of players they represent.

This is effectively what the USTA does with NTRP, using the matches from Nationals to "connect" the different sections, and have those results and how well a section did trickle down to players from the section.  If a section does very well at Nationals, that means relatively speaking the players from that section at that level were rated too low relative to other sections, so player's ratings may go up and more bump ups will occur.  It can go the other way too, and I've pointed out the effect of this in many of my year-end rating analysis'.

I'm guessing the WTN doesn't inherently do this as part of the algorithm, as it seemingly required this significant adjustment to compensate for what they were observing.  Hopefully they still applied the principals of leveling across cohorts and it wasn't entirely manual.

Another challenge the WTN has, and one that doesn't seem to have been addressed yet and wasn't mentioned in the FAQ is gender neutrality.  The algorithm claims to be gender neutral, i.e. just like a WTN 25 male should have a competitive match with another WTN 25 male, either should also have a competitive match with a WTN 25 female.

It is generally accepted that NTRP which is not gender neutral has about a one level (0.5 NTRP) difference between the genders, e.g. a 3.5 male and 4.0 female will be similarly skilled, but looking at WTN ratings one will regularly see men and women of the same NTRP level with similar WTN ratings or even the women having lower (better) WTN ratings.  Similarly, you will see men with higher (better) NTRP levels having higher (worse) WTN ratings.

This means WTN really can't be used to get cross-gender competitive matches today.  And WTN is really handcuffed now when it gets to trying to solve this as it now has to fit both men and women into this compressed 25-40 range I noted above.

For example, looking at men's WTN ratings, leaving room for the 2.5 and 3.0 women to have higher WTN ratings than 3.0 men, and leaving some room for complete beginners not even playing matches yet, the WTN range all recreational men have to fit into is more like 25-35 at best, and perhaps even less.

The change made to WTN may very well make it better than before.  But the challenges of truly being a world tennis number are still there.  It will be interesting to see how it continues to mature.

Has the ITF updated the WTN algorithm? Is it any better?

I received an e-mail today from the USTA titled "Now Here: Updates to ITF World Tennis Number" and it goes on to describe the ITF on-boarding several new federations, but also says the ITF has taken the opportunity to "enhance the ITF WTN calculation" and as a result player's WTNs may change.

I've written about the WTN before (see a list of all WTN related posts here) and done some analysis (men's singles, women's singles, men's doubles, women's doubles) that raised some questions about its accuracy.  Since then, I haven't written that often as 1) the ITF/USTA have made it difficult to gather data to do analysis and 2) casual monitoring showed the same initial observations still stood.  This new announcement may cause me to revisit things, although it may be hard to do so broadly.

An initial/personal look though reveals there have been some big changes!

I'd had a WTNs of around 13 forever based on singles play from years ago, and checking today, I see my WTNs is now 26.9!  I'd say that is a change.

In doubles, I've been around a 22 WTNd and today, 29.2!

Whoa, overnight I've gotten a lot worse!

For reference, I'm a middling 4.5 playing primarily (only lately) doubles with a few wins in men's this year but more losses, although several were in match tie-breaks.  Even if NTRP were to bump me down to 4.0 at year-end, the new WTN algorithm seems to be saying that I as a 4.0/4.5 male is a 26.9 WTNd.

If this is done across the board and it is consistent, perhaps it is better, relatively at least, but on the surface the mapping between NTRP and WTN seems even worse than before now.  A 4.5 male at 26.9 doesn't leave a lot of room for the 2.5-4.0 players, and there is a lot of room for the 4.5-7.0 players.

Looking at some players around me, I've recently been playing 8.0 mixed with 3.5 women partners, and have done better (4-1 this season) and WTNd had my partners similarly rated to me, around 21-24.  That screams that something is wrong with the gender neutral part of WTN, and this algorithm change as my 3.5 women partners are still similarly rated to me, 28-32 or so.

I'm sure there will be naysayers out there who say I must be playing like a 3.5 woman, perhaps that is true, but then the folks I've beat must be at that level or worse.

So there seems to have been a blanket shift up numerically (down in rating strength as WTN has 1 as the best and 40 as the worst) to give more room for high rated players, but no significant change to making gender neutral relativity more accurate.

I'll try to do some more analysis later, but what are you seeing?  What do you think?  Is WTN even something relevant to you in any way at this point?

WTN lookup now available on ITF's site with additional features

After many e-mails from the USTA about it, the ITF World Tennis Number (WTN) was rolled out on usta.com about a month ago, and today I got an e-mail that it is now available on the ITF's worldtennisnumber.com site.

The player search page has a footnote that it is currently only showing USTA players.  I'm not sure why this is as the LTA launched WTN about six months ago so you'd think those players could be available too, but at least for now they aren't.

The search is interesting in that it seemingly only lets you search by surname (last name) or a tennis ID.  The type ahead last name search isn't terribly useful as there are often many players with the same last name and the player you are looking for may not be in the four they show.  So you have to finish your search and get the full list which can then be filtered by gender, country, and singles or doubles WTN.  This is an interesting way to search as if you knew the WTN, you probably wouldn't be looking!

But you can put in a range and narrow it down and presumably find who you are after, at which point you can click on them and get a page that is similarly branded to what the USTA sites shows, but with more detail!  The same animated WTN widget is there with singles and doubles WTN and Game zONe numbers, but on the overview page you additionally get:

• Match activity with a count of unique singles opponents, average singles interval, and average doubles interval
• Rating range that can show the range for singles and doubles for all time or the past year
• A chart of "player tournament matches" showing the count of wins and losses by month, filterable by singles or doubles, although it does appear to include USTA League matches too, not just tournaments
• A results summary with the win-loss record which can be filtered by singles/doubles/both and different time periods

Based on the results summary, it does appear it includes matches, for me at least, that were played in 2016, so I'm guessing that is roughly when the data starts the USTA provided to the ITF, which is consistent with what we've seen/heard elsewhere.  In fact, one can go to the Results tab and there, the date filter goes back to July 1st, 2016 so that appears to be the start date for WTN.

The Results tab is also where you can see more details with the specific matches including the players, their WTN, and the score.  They are actually grouped by event/league which is kind of nice, but oddly had a a stray match that wasn't in the right league.  The WTN shown does seem to be the WTN at the time of the match, so you can see how it changes.

Then there is a Head to Head tab where you can search for another player and see a head to head comparison of WTN ratings and if they've played, the records.  It seems to only do this for singles matches though so you can't find your stats with a partner or against a doubles opponent.  It will also show competitors in common which may be useful if you are scouting a future opponent.

All in all it is a nice presentation and it does provide more information than the USTA's site does and adds some additional useful context to help understand more about your WTN and playing history.

What does WTN do with professionals, and what is the Pro Zone?

The World Tennis Number (WTN) from the ITF is now being published on USTA player profiles, is advertised as a rating going from 40 for a beginner, to 1 for a pro.  But what exactly does that mean?  What are professional's WTNs?  And how can I relate a pro's WTN to your own?

First, from the various FAQs on WTN, there is the text "Pro players will be closer to 1".  This isn't explicit, but with the FAQ preceding this statement with the range being 40 to 1, one might think that the very top pro is a 1.0 and other pros would be in the 1.x or perhaps even 2.x range.

Second, in my perusal of WTNs, the smallest I've seen is 1.1, this for a male unrated (NTRP) player from Mississippi.  There are actually very few in the 1's, but the 2's has a fair number.  So if a pro is a 1, is this 1.1 on par with pros?

When I did my chart showing a hypothetical mapping from NTRP to WTN, I left a little room for pros (NTRP 7.0) to live in the 1-3 WTN range.  My guess at the mapping has been proven wrong with the ranges much larger with huge overlap, but if there is no room for the pros, what is done for them?

It turns out, the USTA at least, is not publishing WTNs for pros.  If you go lookup Jack Sock for example, you won't see a WTN showing for singles or doubles, but instead it has the meter maxed out and "Pro Zone" text in the middle of the widget.

It appears what happens is anyone that is an actual "pro", this based on having an ATP/WTA ranking, will simply be listed as a "Pro" and that appears to be what "Pro Zone" means.  This from an LTA web-site:

A world-wide rating system that ranges from 40 (recreational players) to 1 (pro players) - players with an ATP/WTA ranking will be listed as PRO

What I'm not sure of is if the matches professionals play are part of the WTN dataset or not.  You'd think they would be, in which case my guess is the WTNs could go below 1.0 and perhaps even negative.  Perhaps this is why they don't show them and instead just show "Pro Zone".

But what will happen when Jack quits playing and his ATP ranking goes away?  Shouldn't his WTN then become visible?  What will it be?

This exposes a bit of a challenge for any rating system where there are arbitrary upper and lower thresholds.  What happens if a 39.9 does so poorly that their calculated WTN goes above 40?  What happens when a player, recreational player or pro, wins so much their WTN goes below 1?  Does the whole range have to be recalibrated and everyone's WTN changes to keep the integrity of the 40 and 1 boundaries?

It appears the ITF (or USTA at least) is punting on the subject and just not showing pro's WTNs.  And beginners, at this point at least, aren't playing any matches that get into the system so we don't have to worry about that yet.

Although on this last point, I do see some NTRP 2.5s  with WTNs of 40.0, not many, but a few.  So it appears this boundary is enforced, at least from what is published.

And in another "Whacky WTN" moment, I found a male player who is a self-rated NTRP 5.5, and in singles they show as "Pro Zone", but in doubles they are a measly 22.3 which is the WTN you might see for an NTRP 3.5 or even 3.0 player!  Similarly I found a female player with no NTRP that is "Pro Zone" in singles but a WTN 17.4 in doubles.  And there are others that are Pro Zone in singles or doubles and a double digit WTN in the other.  And some of these wild differences have the high confidence blue checkmark as well.

I'm sure some of what I'm seeing are exceptions or edge cases, but I'm coming across a fair amount.  It is interesting to say the least.

Observations about WTN for USTA League players after two weeks of publishing

The USTA has now published the new World Tennis Number (WTN) for two weeks, so there is enough data, real and anecdotal, to begin making some observations.

As stated by the ITF/USTA, a player's WTN is supposed to be updated once a week on Wednesday and incorporate matches through the previous Sunday.  So far we've had the ratings published on Wednesdays so they are hitting that, but are they incorporating the matches they say there are?

That leads to the first observation which is it appears there may be a delay in matches being included.  I've seen several cases where players played matches between 6/5 (the previous Sunday) and 6/12 (the Sunday before the 6/15 publish) and all indications are those matches were not included in the calculations.  And yes, I checked, the matches were entered on time and prior to 6/12.

This may just be growing pains and it will get ironed out, but if a player's matches are not consistently included, it makes it difficult to follow one's WTN and derive any meaning or benefit from tracking it.

But on the other side, there are players that played no new matches, and their WTN changed from week one to week two.  This isn't right or wrong, but does perhaps give us some insight into the algorithm.  It is possible that the matches included actually changed due to catching up, despite none being played, and this would be another indication of some growing pains in the data collection, but it is perhaps more likely that the WTN algorithm simply allows for changes to a player's rating when they don't play due to prior opponents playing and their rating going up or down.

It is a classic debate with ratings algorithms on if one should only look at the rating of the opponent at the time of the match, or if their future results, and them getting better or worse, should have an effect on your rating.  As I understand it, the dynamic NTRP rating calculated throughout the year only looks  at the rating at the time of the match and your dynamic rating won't change if you don't play.  UTR on the other hand will have a player's rating change when they don't play (wildly so at times) and it appears WTN is following UTR's lead in this area.  I have not seen wild swings with WTN, but we only have one update's worth of data.

A big observation I perhaps should have led with is that in mapping NTRP to WTN, you end up with some extremely large ranges.  I showed this in my analysis of singles (men and women) and doubles (men and women) mappings, but the summary is that doubles has a wider range than singles, but even singles has one NTRP level mapping to 10+ WTN levels (doubles has 15+).  A side-effect of this is that some WTN levels have noticeable representation from 3-4 NTRP levels.  If WTN is to be believed, these players from the 3-4 NTRP levels would have a competitive match together.

Another observation is that some players have dramatically different singles and doubles WTNs.  Differences of 5 are not uncommon at all and there are some that are 10 or more different.  And from personal experience, some of the differences are way off and perhaps even backwards.

Note that WTN is arguably better than NTRP in that it calculates separate ratings for singles and doubles, and the majority of players are probably better at one than the other.  The question is if what the WTN is calculating reflects reality or not.  Perhaps it does overall but there are at least some exceptions that make you go hmmm.  But the separate ratings can also be an explanation for some, but not all, of these observations.

WTN has been positioned as a gender neutral rating, but from what we are seeing, in part due to the really wide ranges noted above, there are women that are two or three NTRP levels lower than some men, that have better WTN ratings than the men.  For example, a 3.5 woman with a WTN that is 2 levels better than a 4.5 man.  It seems improbable that this is accurate, but NTRP has its edge case issues too so I wouldn't throw WTN out because of this, but something seems off.

Note that WTN has said it uses data from four years back, and perhaps even started using data six or more years back, so I don't think it being new and lack of data is an explanation.  I would have thought the observations I'm making would have been made during development and addressed if possible.  Perhaps WTN doesn't consider any of these to be an issue.

Given all these observations, I'm not sure a USTA League player will find WTN terribly valuable.  It is clearly different than NTRP, sometimes significantly higher or lower than expected, and your WTN going up or down or being at a certain level may give no indication of whether you will be bumped up or not which is what a lot of players care about.  Since the USTA says NTRP isn't going away, WTN may be just a curiosity for players to follow for fun.

And since it appears there are some clear inconsistencies in the mapping and ranges, the promise of the WTN Game zONe being a good indicator of a competitive match may or may not be accurate right now.

What do you think?  How much attention are you going to pay to your WTN?

Week two of WTN for USTA players

It has been a week since the USTA began publishing WTN ratings for players, and right on schedule it appears the weekly update is being pushed out.  Kudos to the USTA and ITF for sticking to the schedule as advertised.

I've only been able to do some anecdotal analysis of the new ratings so far, more details to hopefully come soon, but I've noticed a few things.

• WTN ratings can change without a player playing additional matches
• Correspondingly Game zONe and confidence levels can also change without a player playing additional matches
• For these players, changes I've seen are generally in the single-digit hundredths, but there are some with larger changes, the highest I've seen is 0.7.

It is entirely possible that while a player did not play more matches, something was reported late to the USTA or ITF and so the algorithm sees it as an additional match and that is why a rating changed.  However, I suspect instead there is some factor in the algorithm that gives more weight to recent results, or has results in the past fall outside the window being considered, or there is an iterative/retroactive aspect to the algorithm and while a player didn't play, someone they played in the past did play and that affected their rating.

If you want to see all the analysis I've done on WTN recently, click here and scroll through the list of posts.

Mapping NTRP to WTN - Men's Singles

The USTA has started publishing the new World Tennis Number (WTN) for players on their profile on usta.com.  I did some initial analysis last week, but now I'm able to do a bit more thorough and complete analysis so this begins a sequence of posts with that.

My process for this analysis is to look at a sampling of the USTA League players who received a 2021 year-end rating/level and look at the distribution of WTN levels for each different gender, discipline, and level.

By limiting it to players that received a 2021 year-end level I am only considering players who got a recent NTRP rating so that I'm not using stale NTRP levels in the comparison.  Since NTRP levels don't change again until the end of 2022, a player could have gotten better or worse in the 6 months since ratings were published, but this seems like a reasonably consistent approach to doing this mapping.  Ideally this would be done using WTN ratings at the time the NTRP ratings were published, but we haven't had WTN until now so we do the best we can.

In this post, I'm looking at WTN's for men's singles.  What you will see in the chart below is the count of players at each WTN level in total and broken out by NTRP level.  So let's have it!

(You likely want to click on the image to see a larger version of it).

Looking at the general distribution, we see a typical normal distribution to the left of WTN 17, but there isn't a true peak in the middle, and to the right of 20 there are some strange drops.  It is certainly possible this is the skill level profile of men doubles players, and it could be that the players that would be in the long tail aren't playing competitive matches and so aren't in the WTN system.

We also see as you move towards single digits, there isn't the strange blip that the men's doubles had.

The above is including all players, but if we limit it to those with a high confidence WTN, the chart is at follows:

This looks a bit better, but a bit of a strange step from 14 to 16.

What is dramatically different is the number of players drops over 85%.  It would seem there are very few men that play enough singles to get a high confidence WTN.

But looking at the counts by NTRP level is what is perhaps more interesting and will give us an idea of how NTRP maps to WTN.

As you'd expect there is for the most part the expected normal curve within each level.  What is perhaps not expected is how wide each NTRP level is, although they are probably not as wide as the doubles players.

There are a reasonable number of 4.5s ranging from 8 to 18 with an average of 13.6 and standard deviation of 2.6.  If there was a direct and perfect conversion from NTRP to WTN, one NTRP level would correlate with about 4 WTN levels, so having a range of 11 levels, with some players even beyond that, seems a little high.

Similarly, there are a reasonable number of 4.0s from 11 to 22 with an average of 16.8 and standard deviation of 2.6.  Both of these are significantly better than the doubles and approaching what you might expect.

The other thing you can do with this chart is see how many NTRP levels there are at a given WTN level.  For example WTN 18 has a noticeable segment of players from 3.0 to 4.5.  If WTN were to be right, it would be saying the 3.0s and 4.5s with WTN 18 would have a competitive match.  That seems hard to believe, but perhaps there really are some edge cases where a 4.5 has a rating that is lagging their ability and the WTN algorithm, despite being updated weekly, hasn't caught up with the 3.0's improvement.  But this seems a bit of a stretch.

Which is right?  WTN or NTRP?  I can't say at this point, but stay tuned, I'll keep doing analysis.  And it is likely that neither is "right" or "wrong" and they are just different.

See the prior post for Women's Doubles, Men's Doubles, and Women's Singles.

Mapping NTRP to WTN - Women's Singles

The USTA has started publishing the new World Tennis Number (WTN) for players on their profile on usta.com.  I did some initial analysis last week, but now I'm able to do a bit more thorough and complete analysis so this begins a sequence of posts with that.

My process for this analysis is to look at a sampling of the USTA League players who received a 2021 year-end rating/level and look at the distribution of WTN levels for each different gender, discipline, and level.

By limiting it to players that received a 2021 year-end level I am only considering players who got a recent NTRP rating so that I'm not using stale NTRP levels in the comparison.  Since NTRP levels don't change again until the end of 2022, a player could have gotten better or worse in the 6 months since ratings were published, but this seems like a reasonably consistent approach to doing this mapping.  Ideally this would be done using WTN ratings at the time the NTRP ratings were published, but we haven't had WTN until now so we do the best we can.

In this post, I'm looking at WTN's for women's singles.  What you will see in the chart below is the count of players at each WTN level in total and broken out by NTRP level.  So let's have it!

(You likely want to click on the image to see a larger version of it).

Looking at the general distribution, we see a typical normal distribution to the left of WTN 22, but to the right, things aren't quite as prototypical.  There is a spike at 23 and then several big dropps to 24, then to 26 and also 28.  It is also missing the long tail we expect from a normal distribution.  It is certainly possible this is the skill level profile of women doubles players, and it could be that the players that would be in the long tail aren't playing competitive matches and so aren't in the WTN system.

We also see as you move towards single digits, the women fall off quickly.  Below WTN 15, there are very few players, even though the peak in singles is 23 while the doubles peak was 25, the long tail to the left was more significant for doubles than singles.

The above is including all players, but if we limit it to those with a high confidence WTN, the chart is at follows:

This isn't dramatically different looking, but the peak is at 20 instead of 23.  What is dramatically different is the number of players drops over 80%.  It would seem there are very few women that play enough singles to get a high confidence WTN.

But looking at the counts by NTRP level is what is perhaps more interesting and will give us an idea of how NTRP maps to WTN.

As you'd expect there is for the most part the expected normal curve within each level, perhaps more so than the doubles analysis.  What is perhaps not expected is how wide each NTRP level is, although they are probably not as wide as the doubles players.

There are a reasonable number of 4.5s ranging from 13 to 22 (10 to 24 for all) with an average of 16.1 and standard deviation of 2.2.  If there was a direct and perfect conversion from NTRP to WTN, one NTRP level would correlate with about 4 WTN levels, so having a range of 10 levels, with some players even beyond that, seems a little high.

Similarly, there are a reasonable number of 4.0s from 15 to 26 (12 to 29 for all) with an average of 18.6 and standard deviation of 1.9.  Both of these are significantly better than the doubles and approaching what you might expect.

The other thing you can do with this chart is see how many NTRP levels there are at a given WTN level.  For example WTN 21 has a noticeable segment of players from 3.0 to 4.5.  If WTN were to be right, it would be saying the 3.0s and 4.5s with WTN 21 would have a competitive match.  That seems hard to believe, but perhaps there really are some edge cases where a 4.5 has a rating that is lagging their ability and the WTN algorithm, despite being updated weekly, hasn't caught up with the 3.0's improvement.  But this seems a bit of a stretch.

Which is right?  WTN or NTRP?  I can't say at this point, but stay tuned, I'll keep doing analysis.  And it is likely that neither is "right" or "wrong" and they are just different.

See the prior post for Women's Doubles and Men's Doubles, and stay tuned for the Men's Singles.

An Update to Mapping NTRP to WTN - Men's Doubles

I wrote yesterday about some observations from looking at WTN levels by NTRP level for men's doubles players, and key one being that the range of WTN levels for each NTRP level was quite large.  After giving it some thought, I wanted to make a slight adjustment to what I did to perhaps be a little more fair to WTN.

My approach to the analysis was to look at players that had a 2021 year-end 'C' NTRP rating/level and look at the WTN's for these players.  The idea was that if the USTA was able to give the player a 'C' rating, it should be good enough for WTN too.

Upon looking deeper, I found that a fair number of players I looked at did not have the blue check mark indicating a high confidence in their WTN rating, so it only seemed fair to take another pass at the analysis to only include those with a high confidence.

On to the new chart then!

For comparison, here is the previous chart.

The new chart does look a bit better, the unexpected non-"normal" right half of the chart now looks better.  So it would seem it was low-confidence players that were not rated accurately and causing the strange looking chart.

However, we see the counts at each WTN are down nearly 50%, so about half of the players that NTRP found had enough matches to get a 'C' rating, WTN does not give a high confidence rating.  Now, this is in part because WTN calculates separate singles and doubles ratings so that shouldn't be ignored.

The blip at WTN 3 is still there, but it is smaller and there are fewer 4.5s in it which is an improvement.

While the above few things are improved, the ranges of WTN levels for an NTRP level are still very large.  At 4.0 for example, we still see significant numbers of players from 13 to 27 which is 15 levels, still more than I would have expected.

Standard deviations came down a bit but are still pretty large:

• 3.0 went from 3.4 to 3.2
• 3.5 went from 3.7 to 3.4
• 4.0 went from 4.1 to 3.5
• 4.5 went from 4.9 to 3.9

A modest to decent improvement, but still larger than I'd expect.

So I thought it was only fair to use high confidence WTNs, but the observations don't change a whole lot.

What do you think?

An Update to Mapping NTRP to WTN - Women's Doubles

I wrote yesterday about some observations from looking at WTN levels by NTRP level for women's doubles players, and key one being that the range of WTN levels for each NTRP level was quite large.  After giving it some thought, I wanted to make a slight adjustment to what I did to perhaps be a little more fair to WTN.

My approach to the analysis was to look at players that had a 2021 year-end 'C' NTRP rating/level and look at the WTN's for these players.  The idea was that if the USTA was able to give the player a 'C' rating, it should be good enough for WTN too.

Upon looking deeper, I found that a fair number of players I looked at did not have the blue check mark indicating a high confidence in their WTN rating, so it only seemed fair to take another pass at the analysis to only include those with a high confidence.

On to the new chart then!

For comparison, here is the previous chart.

The new chart does look better, the unexpected non-"normal" right half of the chart now looks better.  So it would seem it was low-confidence players that were not rated accurately and causing the strange looking chart.

However, we see the counts at each WTN are down over 30%, so about half of the players that NTRP found had enough matches to get a 'C' rating, WTN does not give a high confidence rating.  Now, this is in part because WTN calculates separate singles and doubles ratings so that shouldn't be ignored.

While the above few things are improved, the ranges of WTN levels for an NTRP level are still very large.  At 4.0 for example, we still see significant numbers of players from 15 to 26 which is 12 levels, still more than I would have expected.

Standard deviations came down a bit but are still pretty large:

• 3.0 went from 3.1 to 2.9
• 3.5 went from 3.2 to 2.9
• 4.0 went from 3.3 to 3.0
• 4.5 went from 3.8 to 3.3

A small/modest improvement, but not a dramatic change.

So I thought it was only fair to use high confidence WTNs, but the observations don't change a whole lot.

What do you think?

Mapping NTRP to WTN - Men's Doubles

The USTA has started publishing the new World Tennis Number (WTN) for players on their profile on usta.com.  I did some initial analysis last week, but now I'm able to do a bit more thorough and complete analysis so this begins a sequence of posts with that.

My process for this analysis is to look at a sampling of the USTA League players who received a 2021 year-end rating/level and look at the distribution of WTN levels for each different gender, discipline, and level.

By limiting it to players that received a 2021 year-end level I am only considering players who got a recent NTRP rating so that I'm not using stale NTRP levels in the comparison.  Since NTRP levels don't change again until the end of 2022, a player could have gotten better or worse in the 6 months since ratings were published, but this seems like a reasonably consistent approach to doing this mapping.  Ideally this would be done using WTN ratings at the time the NTRP ratings were published, but we haven't had WTN until now so we do the best we can.

In this post, I'm looking at WTN's for men's doubles.  What you will see in the chart below is the count of players at each WTN level in total and broken out by NTRP level.  So let's have it!

(You likely want to click on the image to see a larger version of it).

Looking at the general distribution, we see a fairly typical normal distribution to the left of WTN 22, but to the right, things aren't quite as prototypical.  22 itself is more of a peak than expected, with a quick drop to 23 and 24 before a normal gradual slope, then a quick drop again, and then it is missing the long tail we expect from a normal distribution.  It is certainly possible this is the skill level profile of male doubles players, and it could be that the players that would be in the long tail aren't playing competitive matches and so aren't in the WTN system.

There is an odd blip of men at WTN 3, including some 4.5s, more at WTN 3 than at any of WTN 4 thru 8.  That seems a bit odd, both the 4.5s/5.0s and the high (relatively) number.

Comparing this to the women's chart, we see there is a different in both the WTN with the largest number, 22 for the men and 25 for the women, but also where the women had virtually no one at 10 or better, the men have a fair number including the blip at 3.

But looking at the counts by NTRP level is what is perhaps more interesting and will give us an idea of how NTRP maps to WTN.

As you'd expect there is for the most part the expected normal curve within each level, that is until you get to 3.0 which has some ups and down across WTNs that causes the oddity noted above.  What is perhaps not expected is how wide each NTRP level is.

There are a noticeable number of 4.5s ranging from 3 to 27 (2 to 31 for all) with an average of 17.2 and standard deviation of 4.9.  If there was a direct and perfect conversion from NTRP to WTN, one NTRP level would correlate with about 4 WTN levels, so having a range of 25 (!!!!) levels, with some players even beyond that, seems very high.

Similarly, there are a reasonable number of 4.0s from 10 to 30 (3 to 34 for all) with an average of 21.4 and standard deviation of 4.09.

The explanation of course is that NTRP and WTN use different algorithms and there is no direct mapping.  And WTN could argue that their algorithm is better and these large ranges are actually correct and more accurate, but that would be indicting NTRP as not being accurate then.

One key algorithm difference is that WTN calculates separate singles and doubles ratings, and that can certainly be the reason for some variance, e.g. someone could be good at doubles and bad at singles but play both.  Their NTRP will be somewhere in the middle but WTN will have the individual ratings farther apart.

Additionally, what matches the USTA includes for WTN has not, to my knowledge, been shared yet.  If WTN includes matches that NTRP does not, that could be contributor to differences between the two systems.

Back on the genders though, comparing the average WTN for males and females, we get:

• 3.0 - women 28.2 vs men 28.4
• 3.5 - women 24.8 vs men 24.6
• 4.0 - women 21.9 vs men 21.4
• 4.5 - women 18.7 vs men 17.2

There is not a significant difference between these at most levels, then men being a few hundredths better at 3.5 and 4.0, and 1.5 better at 4.5, but surprisingly the average 3.0 woman rates better than the average 3.0 man!  Something seems amiss here as there is a general consensus that on the NTRP scale the male and female of the same level, the male is about 0.5 NTRP better.  That would translate to about 2 WTN levels and we see the difference at 4.5 approaching that, the other levels it does not.  I'm not sure the gender neutrality part of WTN is fully working yet.

The other thing you can do with this chart is see how many NTRP levels there are at a given WTN level.  For example from WTN 20 to 27 there are 4 or perhaps even 5 noticeable segment of players from 2.5/3.0 to 4.5.  If WTN were to be right, it would be saying the 3.0s and a 4.5s with WTN 25 would have a competitive match.  That seems hard to believe, but perhaps there really are some edge cases where a 4.5 has a rating that is lagging their ability and the WTN algorithm, despite being updated weekly, hasn't caught up with the 3.0's improvement.  But this seems a bit of a stretch.

Which is right?  WTN or NTRP?  I can't say at this point, but stay tuned, I'll keep doing analysis.  And it is likely that neither is "right" or "wrong" and they are just different.

See the prior post on Women's Doubles, and stay tuned for this same post for the Women's Singles, and Men's Singles.

Update: I did an update that only looked at high confidence WTN ratings here.

Mapping NTRP to WTN - Women's Doubles

The USTA has started publishing the new World Tennis Number (WTN) for players on their profile on usta.com.  I did some initial analysis last week, but now I'm able to do a bit more thorough and complete analysis so this begins a sequence of posts with that.

My process for this analysis is to look at a sampling of the USTA League players who received a 2021 year-end rating/level and look at the distribution of WTN levels for each different gender, discipline, and level.

By limiting it to players that received a 2021 year-end level I am only considering players who got a recent NTRP rating so that I'm not using stale NTRP levels in the comparison.  Since NTRP levels don't change again until the end of 2022, a player could have gotten better or worse in the 6 months since ratings were published, but this seems like a reasonably consistent approach to doing this mapping.  Ideally this would be done using WTN ratings at the time the NTRP ratings were published, but we haven't had WTN until now so we do the best we can.

In this post, I'm looking at WTN's for women's doubles.  What you will see in the chart below is the count of players at each WTN level in total and broken out by NTRP level.  So let's have it!

(You likely want to click on the image to see a larger version of it).

Looking at the general distribution, we see a typical normal distribution to the left of WTN 25, but to the right, things aren't quite as prototypical.  There is a significant drop from 25 to 26 and 27, and then is somewhat as expected through 33, but then it is missing the long tail we expect from a normal distribution.  It is certainly possible this is the skill level profile of women doubles players, and it could be that the players that would be in the long tail aren't playing competitive matches and so aren't in the WTN system.

We also see as you move towards single digits, the women fall off quickly.  While there are a good number of women with a WTN of 20, less than a quarter of that number are a WTN 15 and at 12 or lower, there are hardly any.  It will be interesting to compare this chart with the men's to see how different it is, which will give us an idea of how WTN handles gender neutrality.

But looking at the counts by NTRP level is what is perhaps more interesting and will give us an idea of how NTRP maps to WTN.

As you'd expect there is for the most part the expected normal curve within each level, that is until you get to 3.0 and 2.5, where it doesn't tail off at the higher WTNs as noted above.  What is perhaps not expected is how wide each NTRP level is.

There are a reasonable number of 4.5s ranging from 12 to 26 (4 to 32 for all) with an average of 18.7 and standard deviation of 3.8.  If there was a direct and perfect conversion from NTRP to WTN, one NTRP level would correlate with about 4 WTN levels, so having a range of 15 levels, with some players even beyond that, seems very high.

Similarly, there are a reasonable number of 4.0s from 15 to 29 (4 to 33 for all) with an average of 21.9 and standard deviation of 3.3.

The explanation of course is that NTRP and WTN use different algorithms and there is no direct mapping.  And WTN could argue that their algorithm is better and these large ranges are actually correct and more accurate, but that would be indicting NTRP as not being accurate then.

One key algorithm difference is that WTN calculates separate singles and doubles ratings, and that can certainly be the reason for some variance, e.g. someone could be good at doubles and bad at singles but play both.  Their NTRP will be somewhere in the middle but WTN will have the individual ratings farther apart.

Additionally, what matches the USTA includes for WTN has not, to my knowledge, been shared yet.  If WTN includes matches that NTRP does not, that could be contributor to differences between the two systems.

The other thing you can do with this chart is see how many NTRP levels there are at a given WTN level.  For example WTN 25 has a noticeable segment of players from 2.5 to 4.5.  If WTN were to be right, it would be saying the 2.5s and a 4.5s with WTN 25 would have a competitive match.  That seems hard to believe, but perhaps there really are some edge cases where a 4.5 has a rating that is lagging their ability and the WTN algorithm, despite being updated weekly, hasn't caught up with the 2.5's improvement.  But this seems a bit of a stretch.

Which is right?  WTN or NTRP?  I can't say at this point, but stay tuned, I'll keep doing analysis.  And it is likely that neither is "right" or "wrong" and they are just different.

And stay tuned for this same post for the Men's Doubles, Women's Singles, and Men's Singles.

Update: I posted an update that looks at only high confidence WTNs here.

Initial analysis of NTRP to WTN mapping - Much larger ranges than you'd think!

The USTA launched showing player's WTN on their profile earlier this week and I made some anecdotal observations yesterday, but have now started to do a more scientific analysis and while it is by no means complete, I wanted to share some initial results from it.

For this analysis I'm looking at male players with a 4.0C or 4.5C year-end rating for 2021.  The theory is that since NTRP is only published once a year, this is the most recent rating/level and should be the most relevant to compare with.  Yes, I'm doing the same for 4.0 and 4.5 females, it will come shortly.

With this population of players, I can then look at the range of WTNs for each level to see how things map in practice.  I've included the average and standard deviation here too:

• 4.0 singles - range: 32.2 to 4.4, average: 17.6, standard deviation: 3.2
• 4.0 doubles - range: 34.0 to 3.3, average: 21.4, standard deviation: 4.1
• 4.5 singles - range: 32.3 to 5.1, average: 14.4, standard deviation: 3.4
• 4.5 doubles - range: 31.1 to 2.4, average: 17.2, standard deviation: 4.9

The first thing that jumps out is some pretty astonishing ranges.  If a single NTRP level can span up to 30 WTN levels, it makes interpreting a WTN very difficult to say the least.  It could of course be that WTN is far better and the NTRP levels for these players is way off as well, but ranges this large make you go hmmm and require further analysis.

On the other hand, the averages do kind of make sense.  It is interesting that within a level, the singles WTN is significantly better than doubles, in fact on average this has a 4.0 singles player being rated about the same as a 4.5 doubles player.  Given there are separate singles and doubles ratings, I don't know that one can actually compare them as I'm not sure there is any correlation between them.

But the wide ranges could be due to a handful of edge cases and the general population is more consistent.  The standard deviations help here and, assuming a normal distribution, means that about 68% of 4.0 singles ratings are going to be between 20.8 and 14.4, and that is a lot more palatable, but still 68% leaves a significant number outside of that range.  And that range is wider than the Game zONe (generally about +/-2) meaning even by the USTA's definition, some portion of this 68% won't be evenly matched, let alone those outside of it.  And the doubles standard deviations are significantly higher.

But, the above is looking at all players.  The WTN does have a confidence number that is presumably based on number of matches played and gets higher (up to 100) as the algorithm considers a WTN to be more accurate.  If I do the same stats as above but for WTNs with a confidence of 70 or higher, it is better but still broad ranges.

• 4.0 singles - range: 27.4 to 10.1, average: 16.8, standard deviation: 2.6
• 4.0 doubles - range: 31.7 to 3.9, average: 20.4, standard deviation: 3.5
• 4.5 singles - range: 25.7 to 6.7, average: 13.7, standard deviation: 2.6
• 4.5 doubles - range: 28.4 to 3.3, average: 15.8, standard deviation: 3.9

It is interesting that the average gets better in every case by around a point as the confidence gets higher.  The standard deviations drop but are still above the +/-2 the Game zONe tends to be.

More analysis to come including getting this data in some charts, but I wanted to share initial observations right away.

The USTA sends their e-mail about the WTN launch

About a month ago, the USTA sent out a bevy of e-mails about the forthcoming World Tennis Number (WTN).  Between May 10 and 13, I received no fewer than five e-mails, with several more in the subsequent couple of weeks.  Then things went silent, and in that quiet WTN's showed up on player's profiles yesterday with no e-mail announcement.

I speculated that an e-mail announcement was forthcoming, and sure enough at 7:58 AM today there it was in my inbox.  No real info in the e-mail other than a link to "See Yours Now" which navigates to your profile on usta.com.

I have not had a chance to do a detailed analysis yet, but initial observations and what I'm hearing is that for many people their WTNs are in the ballpark of what might be expected, but there are a handful of surprises where a doubles or singles WTN is remarkably higher or lower that it perhaps should be, and generally speaking, given that WTN is purported to be gender neutral, there are some female players who have a WTN that is perhaps better than you'd think compared with male players.

Here are a few examples, although I will caveat this with the statement that these are some handpicked examples from what I've seen and certainly don't represent what is happening across the board.

Some interesting gender comparisons:

• 4.5C male with a 21.0 WTNd
• 4.0C female with a 19.7 WTNd
• 3.5C female with an 18.6 WTNd
• 5.0C male with a 16.9 WTNd

This has a 3.5 female less than two points away from a 5.0 male, and both a 3.5 and 4.0 female noticeably better than a 4.5 male.  It is certainly possible that NTRP is lagging (all of these were 2021 year-end levels though) or the fact that WTN has separate ratings for singles and doubles makes it more accurate, but these are interesting.

Then some interesting ranges between singles/doubles:

• 5.0C male with a 5.8 WTNs and 17.8 WTNd
• 4.5C male with a 12.6 WTNs and 21.0 WTNd
• 5.0C male with a 9.5 WTNs and 16.2 WTNd
• 4.5C male with a 13.6 WTNs and 18.7 WTNd
• 5.0C male with a 7.5 WTNs and a 12.3 WTNd
• 4.5C male with a 14.0 WTNs and 18.3 WTNd
• 4.5C male with a 16.7 WTNs and a 21.2 WTNd
• 4.0C male with a 15.8 WTNs and a 20.2 WTNd
• 3.0C male with a 17.0 WTNs and 12.0 WTNd
• 4.5C male with an 18.2 WTNs and a 4.0 WTNd

I ordered these more or less from wildly better doubles WTN to wildly better singles, and there are certainly more where the singles is better, but it isn't always better.  That last one where a 4.5C is a 4.0 WTN in doubles but only an 18.2 in singles is an astonishing range.

It is certainly possible that there are ratings above with very limited results in one discipline or another, but the large ranges are interesting.

What are your observations so far?

The ITF World Tennis Number has been launched for USTA League players!

I've been writing about the ITF World Tennis Number for nearly three years now.  My first post was in July of 2019 when the ITF announced it, and we've been waiting for it to launch ever since.  The pandemic no doubt threw a wrench into the schedule and launch plans, but finally, nearly three years later, it appears to have launched on player's profiles on usta.com.

For those of you used to going to TennisLink for rating or other USTA League related information, that is not where you will go to see your WTN.  Instead, go to usta.com and login to your account there, and then select "Profile" from the menu in the upper right, and it should show you your WTN.  This link may take you there if you are already logged in.

What is surprising is given all the hype the USTA has been whipping up about WTN with all the recent e-mails and webinars, WTN's started showing up with no announcement.  Perhaps it is just rolling out now and an announcement will show up in the next day or two.

Note, as I've written about, you will have both a singles and doubles WTN unlike NTRP where you have just one rating/level that incorporates all play.  The "singles" and "doubles" on the WTN widget on your profile are clickable to switch between seeing the two ratings.

In my case, I play primarily doubles and have a WTN close to where I'd expect given my analysis on a hypothetical mapping between NTRP and WTN.  My NTRP is a 4.5C and my WTN is 21.0 for doubles.  What is surprising is that my singles WTN is 12.6!  While I like to play singles, at this point, I am almost certainly a better doubles player and clearly my WTN does not reflect this.  This may be an indication of some issues with the WTN algorithm.

What is also interesting is my doubles WTN does not have the Game zONe but my singles does, despite no singles matches in league play recently.

What NTRP are you and what is your singles and doubles WTN?  Do your WTN ratings make sense?  Or does something seem amiss?

Update on 2022 USTA League Nationals, Oklahoma City is back in! And more on WTN

I learned yesterday that one of the sites for 2022 USTA League Nationals has changed.  While the Nationals page/schedule on usta.com has not been updated as of when I'm writing this, it is forthcoming and you can expect to see the events originally scheduled for Tucson to now be in Oklahoma City.  I've updated my prior post so it is (hopefully) now correct.

I also got another e-mail from the USTA on WTN.  It was another "almost here" e-mail with links to I believe the same FAQ and other resources.  I'm expecting WTNs to actually be published for USTA members sometime in June.

Last, I did attend a webinar on WTN a few weeks ago, and as expected the focus was nearly entirely on Juniors.  While it will be published for League players as I understand it, NTRP will continue to be used as it is today for all League play and eligibility, at least to start.

What is the WTN Game zONe and how does it and WTN map to NTRP?

I wasn't going to write again on this subject so soon, but the USTA sent out yet another e-mail this morning hyping WTN, so I figured no time like the present to keep the posts going.

The latest e-mail doesn't offer a lot of new information, it just reinforces that NTRP is not going away for League play as a static (for the year) rating/level is more useful for season long competition, but it does offer a downloadable PDF guide/FAQ that summarizes much of the other information out there and that I've written on before.

But on to the new content I have for today!

The USTA will soon be publishing the ITF's World Tennis Number (WTN) for players on their usta.com profile.  While the USTA is saying NTRP is staying put for USTA League, it is still interesting to look at WTN and how we might correlate it to NTRP.

NTRP is purported to offer "compatible" matches between players of the same level.  For example, two 3.5s (3.01-3.50) are considered compatible and should have a reasonably fun and perhaps competitive match with each other.

WTN has what is called the Game zONe which is the range of WTNs a player should be competitive with, in fact they state your winning percentage should be 35-65%, which would seem to be more than compatible and legitimately competitive.

So what is this Game zONe range?  Several examples appear on the WTN info pages I've seen, here is a sampling:

• WTN of 25.4 with a Game zONe of 23.6 to 27.2 (range of 3.6 from -1.8 to +1.8)
• WTN of 24.5 with a Game zONe of 22.7 to 26.8 (range of 4.1 from -1.8 to +2.3)
• WTN of 18.0 with a Game zONe of 16.1 to 19.8 (range of 3.7 from -1.9 to +1.8)

Now, perhaps none of these examples are real, and the inconsistency in the size of the range and offset  from the WTN isn't indicative of what we'll really see.  But if it is close to reality, we can perhaps figure out a mapping from NTRP to WTN and vice versa.

If the WTN "competitive" window is ~4 (+/- 2), the "compatible" window would be a bit larger, say 6 (+/- 3), and NTRP levels being on the 0.5 mean the "compatible" range for NTRP is 0.5.  Which would lead us to believe that a WTN range that is the equivalent of a NTRP level is 3.  If that is true, then there are ~13 levels (3x13 = 39) covering 40 to 1.

Note, it is possible that the Game zONe is actually somewhat variable depending on the WTN, for example, perhaps the zone gets smaller at lower WTNs, i.e. the pro level.

But another way to look at it might be that NTRP ranges from 1.5 to 7.0 and that covers 12 levels.  So if there are 12 NTRP levels and 40 rounded WTN ratings, one NTRP level should span 3.33 WTN levels which is close to the first approach above.

Taking either of these approaches as guidance, we'd have the following potential mapping of NTRP to WTN:

Hypothetical NTRP to WTN Mapping
NTRP	WTN
1.5	40-38
2.0	37-35
2.5	34-32
3.0	31-28
3.5	27-24
4.0	23-20
4.5	19-16
5.0	15-13
5.5	12-10
6.0	9-7
6.5	6-4
7.0	3-1

Note of course that NTRP isn't really used across all those levels as it isn't really calculated for players outside of the 2.5-5.5 range, so whether or not Novak would be right at 7.00 or not is unknown.  And I'm only guessing at how many slots will be reserved for beginners who don't really play competitively to actually have a rating calculated.

I've also taken the liberty of having NTRP levels from 3.0-4.5 cover 4 WTN levels each since that is where the bulk of the players are, and the fringes on the end of the NTRP scale cover 3 WTN levels each which is really just a guess on my part.  Perhaps more differentiation is needed at the pro level and those ranges are larger.

I've also done a discreet mapping from NTRP to WTN above, but the reality is that because the algorithms are different, there may be some overlap when WTNs are published.  For example there may be 3.5s that have WTNs that don't all fit nicely in the 24-27 bucket and there are some WTN 23s or 28s as well that happen to be NTRP 3.5.

So it may be that this math isn't exactly right.  But I do think it gives us a ballpark idea how things may map.  When WTNs are actually published, I will do analysis and see how things map in the real world.

The big thing players will need to get used to is that WTN is "upside down", and as you get better your rating gets lower.  I've noted this early in what I've wrote, but it probably deserves mention again.

What do you think?  If you are primarily a League player, will you follow your WTN or consider it just noise?