The question is simple: Does affirmative action work? The attempt to answer it, however, has created a tangled mass of executive orders, legislative actions, and judicial decisions from Massachusetts to California.
Into this setting comes one of the first comprehensive surveys of affirmative-action data, yielded by dozens of research studies done over several decades. Its conclusion: Affirmative-action programs have been moderately successful, and the trend toward rolling them back is a "costly and dangerous experiment."
The study, by Harvard sociologist Barbara Reskin, comes at a crucial time. In recent years, affirmative action has suffered a backlash propelled …