Are captains in USTA League typically stronger or weaker players? - Interesting tennis league stats

There was recently a question on Talk Tennis asking if captains are generally good players.  Captains are an important part of USTA League and often don't get credit for what they do, and not only handle captaining but play as well.  It seemed interesting to research if they tended to be stronger/weaker for their level, so I did.

I looked at my Estimated Dynamic NTRP Ratings for 2015 and for the 18 & over and 40 & over divisions, for each gender, what the average dynamic rating was for captains vs the average for players rostered by level and gender.  Here is what I found.

For each case, I'm showing the average rating for captains and then the average for players rostered on teams at each level.

Men 18+

3.0 - 2.78 vs 2.74
3.5 - 3.23 vs 3.24
4.0 - 3.68 vs 3.71
4.5 - 4.11 vs 4.15
5.0 - 4.52 vs 4.57

If anything, at levels other than 3.0, the captains are rated slightly lower.

Women 18+

3.0 - 2.76 vs 2.72
3.5 - 3.18 vs 3.18
4.0 - 3.59 vs 3.60
4.5 - 4.01 vs 4.01
5.0 - 4.47 vs 4.48

The gaps here are a lot smaller, other than 3.0 it is in statistical noise.

Women 40+

3.0 - 2.76 vs 2.73
3.5 - 3.19 vs 3.19
4.0 - 3.60 vs 3.61
4.5 - 4.05 vs 4.05

Very similar to the 18+, virtually the same other than 3.0.

Men 40+

3.0 - 2.78 vs 2.78
3.5 - 3.24 vs 3.26
4.0 - 3.68 vs 3.72
4.5 - 4.15 vs 4.21

Similar to 18+, higher levels the captains are a little below the average.

So if you want to look for any generalization, it would be that higher level men's teams are more likely to have captains rated lower than average.  But for women's teams and lower rated men's teams, it is a lot closer and at 3.0, captains may be stronger.

Thoughts?  What is your experience?