Rates of social mobility are some of the most revealing indicators of a society's character. In any society there is a tendency for privileged groups to try to close ranks, preserve their advantages and pass them on to their children, but the arguments of social justice, economic efficiency and social stability all suggest that these tendencies towards closure and inherited privilege should be curbed. In western liberal societies the dominant version of social justice is perhaps the one that advocates equality of opportunity: those with equal effort and talent should be equally rewarded whatever their class, sex, age, race or religion. Economic efficiency likewise requires that workers should be paid according to their actual productivity rather than to ascribed (and economically irrelevant) characteristics such as their race or sex. And theories of social order hold that the blocking of legitimate aspirations for social and economic advancement will be a potent source of social dissent and conflict (see Goldthorpe, 1980; Heath, 1981). On all three counts the opportunities open to members of ethnic minorities are of interest, but sociologically the third has particular interest for whereas within native white society failure to secure upward social mobility may lead to individual responses—to personal frustration and stress—an ethnic minority which experiences discrimination and blocked careers as a shared grievance is to that extent more likely to respond with collective protest and militant group action.