Critics of affirmative action have long said that mismatching black students with colleges that they do not qualify for creates wholly needless academic failures among these students, who drop out or flunk out of colleges that they should never have been in, when most of them are fully qualified to succeed in other colleges.
Has the ending of preferential admissions in the University of California system and the University of Texas system led to a rise in the graduation rates of black students, as critics predicted? Who knows? These universities will not release those statistics.
This is not peculiar to the United States. In Britain, the claim has been repeated endlessly that putting criminals in prison "doesn't work" and that various rehabilitation programs "in the community" are more successful in reducing criminals' repetition of their crimes.
When statistical data from the Home Office showed the direct opposite of what was being proclaimed by the Home Secretary, other high officials, the media, and academics, the solution was simple: Such data were no longer released.
Sometimes it is not the data but the money that is used to limit who can do studies on controversial issues. Advocates of "global warming" have access to all sorts of government research money but skeptics and critics can depend on no such largess and may even be risking their careers by angering bureaucrats who have staked a lot on this crusade and who control the purse strings.
Even when the taxpayers' money is used to collect data or finance research, those who dispense that money and control that data often treat these things as if they were their own private property, to be used to promote research congenial to their own ideologies or interests.