All the same caveats I mentioned before apply again. And again, I scaled things so that the top-400 players would be considered 6.5 or higher.
So here are the WTA top-20 through the end of 2015.
Unlike the men where Djokovic was #1, Serena is not #1 but is instead #3 behind Sharapova and Muguruza. This is because Serena had several closer than expected wins at the US Open and then the loss to Vinci, plus she didn't play the rest of the year while the others did play more and so had a chance to improve their ratings and not lose to Serena. It will be interesting to see how this changes when I include the Australian Open.
The women are quite a bit closer grouped at the top than the men, although there is nearly a 0.5 drop from #1 to #20 which is similar to the men.
Stay tuned for more.
Attribution: Match data is courtesy Jeff Sackmann / Tennis Abstract.