According to an article in New Scientist, the fact that there are so few women in science is all down to numbers. The author Debora MacKenzie explains there is not one woman in New Scientist's list of scientific heroes for 2008, for example. Merim Bilalic of the University of Oxford and colleagues found that statistics can explain the absence of women at the top. "More extreme values are found in larger populations," she says. Individuals at the top are, by definition, rare. In two groups with the same average performance and variability, the larger group is simply more likely to have more of these rare individuals, just because it is larger. The greater the difference in group size, the greater the chance the bigger group will have more exceptional individuals.
To test this idea, Bilalic's team checked the records of the German chess federation – in which males outnumbered females 16 to one. They found that the statistical effect of this difference in numbers accounted for 96% of the observed difference in performance between the sexes. "There is little left for biological differences to explain," says Bilalic. While statistics may explains the absence of females at the top, they don't explain why there are fewer females in the first place. If this is due to any innate differences in chess ability between the sexes it would have to influence whether children start to play the game at all, because the dropout rates for girls and boys once they do start are similar.
Many other factors might keep girls from ever getting into chess, such as cultural expectations, the difficulty of breaking into an activity dominated by boys, or just having been told they're less good at it. "But you can no longer cite the greater number of men among the most successful people as evidence of innate differences until the effects of participation rates have been allowed for," says Bilalic. In short, it's hardly surprising that there are so few women Einsteins when there are so few male ones – because so many more men are in the these fields overall.