America is preoccupied with race statistics--perhaps more than any other nation. Do these statistics illuminate social reality and produce coherent social policy, or cloud that reality and confuse social policy? Does America still have a color line? Who is on which side? Does it have a different "race" line--the nativity line--separating the native born from the foreign born? You might expect to answer these and similar questions with the government's "statistical races." Not likely, observes Kenneth Prewitt, who shows why the way we count by race is flawed.

Prewitt calls for...