Kathleen Thelen explains the historical origins of important cross-national differences in four countries (Germany, Britain, the United States and Japan), and also provides a theory of institutional change over time. The latter is considered a frontier issue in institutionalist analysis, of which there are several varieties emerging from economics, political science, and sociology. Thelen's study contributes to the literature on the political economy of the developed democracies that focuses on different institutional arrangements defining distinctive models of capitalism.