Political crusades, bureaucratic empires and lucrative personal careers as grievance mongers have been built on the foundation of that assumption, which is almost never tested against any facts.
A recent article in the New York Times saw as a problem the fact that females are greatly under-represented among the highest rated chess players. Innumerable articles, TV stories and political outcries have been based on an "under-representation" of women in Silicon Valley, seen as a problem that needs to be solved.
Are there girls out there dying to play chess, who find the doors slammed shut in their faces? Are there women with Ph.D.s in computer science from M.I.T. and Cal Tech who get turned away when they apply for jobs in Silicon Valley?