This is a study of the labor market impact resulting from declining levels of unionization in 18 OECD countries between 1973-1990. Although trade union decline in membership has been carefully recorded, the effects of that decline have not been analyzed previously in the ways proposed here. The research argues that labor market trends are the result of political struggles among workers, employers, and their representatives. It tests hypotheses about the effects of centralized bargaining, the electoral failure of social democratic parties, increased inequality in the work force, and rival economic theories about the oil price shock and the growth of world trade. The mutual dependence of union membership and unemployment is examined using statistical techniques developed by the researcher. Because of the possibility of strong sectoral trends in earnings and employment , the research is supplemented with comparative case studies of Britain, Germany, and the United States, where there are existing data to examine export and sheltered sectors of the national economies. %%% The research will offer new sociological and institutional explanations of important processes of social capital formation that will supplement, if not challenge, existing economic explanations. Through its focus on the struggles by workers and employers to affect economic outcomes, it links stratification research with political sociology and presents the possibility of an enlarged conception of economic sociology.