Thomas Sowell here gives an international perspective to themes from earlier works like Ethnic America and Markets and Minorities. Arguing that major economic and social differences between groups cannot be explained by environment, Sowell asserts that tenacious cultural differences are fundamentally responsible. Using a wide range of evidence from countries and cultures around the world, Sowell notes the persistence of traits among certain ethnic groups under a wide variety of circumstances, suggesting the weak influence of environment. He deals forthrightly with the question of differences in I.Q. between ethnic groups, though unlike Charles Murray and Richard Herrnstein in The Bell Curve, he attributes them more to culture than nature. Despite its international subject matter, the book reflects its author's preoccupation with U.S. domestic issues like affirmative action and multiculturalism.