There was an ethnicity poll not long ago. The board is 99.999% white, +/- a handful of posters. I guess the theme song for this forum should be "white & nerdy."
I didn't read the book, but apparently the recently very popular Freakonomics had some discussion of birth month and a variety of activities, like professional athletes, scientists, etc. Since I didn't read the book I don't know what all their observations were, but I recall a few plausible explanations such as the oldest, most developed kids in a particular grade will appear best to coaches, so they'll be provided more attention, consideration for top positions, etc. -- in addition to whatever benefits they gain directly from growing up as always the most developed and therefore best kids in the class, like self-confidence, practice in the top positions, etc.