[sokoloff]

It doesn't even need that feedback-to-candidates loop to work.

Imagine that the female population of developers is 10%, that they exhibit in every way a performance distribution equal to males in job and interviewing performance, but that every company except yours is half as likely to hire a female candidate as the straight odds would suggest.

The candidate pool as experienced by all companies would consist of more than 10% females (as they would need to apply to twice as many places on average) and the average quality of the female candidate may well be higher than the average male candidate because of the adverse selection at play. (Qualified female candidates are being preferentially passed up in favor of inferior male candidates, leaving the residual female candidate pool more talent-rich than the male pool.)