The last decade has been a time of rapid development in comparative social scientific research on modern welfare states—or more concretely, research on social insurance, pensions, and public assistance policies. Synchronic studies, using highly aggregated measures to make causal inferences about policy developments in all the nations of the world, have declined in favor of longitudinal comparative studies of up to eighteen advanced industrial capitalist democracies. Concomitant with this shift, analytic interest has moved away from industrialization and urbanization and toward more political explanatory variables—including class power and class alliances, the structures of political regimes, political parties, and party systems, and the activities of administrators and policy intellectuals.