All WTA TOP13 is from 13 different countries, and 7 countries is represented into ATP TOP8! Its sound perfect till we take look from which regions they come: EUROPE, EUROPE, EUROPE, EUROPE, EUROPE... all the way!
At WTA TOP64 (WTA PM&P5 and ATP Masters are 64-draw events) there is just 12 non-European players (so in ATP with 20 this kind of distributions are actually better)!
BTW, there is also one bizarre fact about WTA TOP rank this season. For example between Roland Garros and US Open all TOP8 players are also from 8 different countries - but half of them been players with Polish decent, despite only Radwanska represented Poland
(today - 4 out of TOP11).