This paper returns to a classic question of political economy – the zero-sum conflict between capital and labor over the division of the national income pie. A detailed description of labor's share of national income in sixteen industrialized democracies uncovers two long-term trends: an increase in labor's share in the aftermath of World War II, followed by a decrease since the early 1980s. In this paper I propose a model of the relative bargaining power of capital versus labor towards an understanding of the dynamics of labor’s share.