Why Are There So Few Women Chess Grandmasters?

The simple answer: there are less women Chess players. And not, as some studies try to argue, because women ae inherently less intelligent or less spatially adept than men.

So presents Ed Yong at Scienceblog, discussing a paper by Merim Bilalic, chess player and researcher from Oxford University.

Far more men play chess than women and based on that simple fact, you could actually predict the differences we see in chess ability at the highest level. It’s a simple statistical fact that the best performers from a large group are probably going to be better than the best performers from a small one. Even if two groups have the same average skill and, importantly, the same range in skill, the most capable individuals will probably come from the larger group.

(source)