Thanks Justin for time well-spent on your long post.
In the 1990s a former youth bridge organizer in Australia wrote an article quite similar to what Adam wrote here. Being gullible I thought he had a valid point, until Justin's post (and worldwide trends) convinced me that it's normal males to outnumber females at youth bridge - it's not something to worry about.
The top placegetters in America's new 2009 Youth NABC (Under 19, about 36 tables) were almost all (over 90%) male, being names like Adam Kaplan and Kevin Rosenberg, so the trend is likely to continue unless Deb and Michael Rosenberg have any daughters.
Young American females to keep an eye out for in the future might be
Asya Ladyzhensky, Amanda Pham and Madeline Power, but there's not many.
Why would America consistently have slightly less females (less than 10%) among their top youth ranks than many other countries (more like 20%)? It could be that other countries have had National Youth Bridge programs (events) for longer than USA, e.g. Australia has its 42nd annual Youth Week in January, Europe had its 22nd Youth Championships (including their 6th Girls Championships) in Romania this year, but America had only its 2nd Youth NABC in 2009. Still, even in the other countries males still far outnumber females, although I think there was a female pair in Israel's silver medal winning team at the 2009 European U21 Championships.
Peter Gill
Australia