It's great to be open and all, but they never mention what their goal is. Do Google believe diversity is good for workplace cohesion, their own social mobility goals, good corporate moral policy, etc.? The data is interesting in it's own right but I don't better understand where Google is going with diversity; I only understand where Google currently stands.
There could be business goals though: it improves people's public opinion of you and in this case may help protect them from lawsuits.
This link at the bottom of the page has some more info... http://www.google.com/diversity/