The objective of this chapter is to analyze the political economy of failed progressive fiscal reforms in Latin America from a historical perspective, in the post-Keynesian understanding that tax reforms, in the context of scarcity of capital for investment (that characterize the countries of the Latin American periphery despite being rich in natural resources), have a key role in the development process. To this end, the factors related to inequality, both external and internal, are studied, which allows us to understand why successive attempts at progressive fiscal reform have failed in two historical episodes: the Alliance for Progress of the 1960s and the different manifestations of the progressive tide during and after the last supercycle of commodities. In this sense, the contribution recovers the discussion on structural heterogeneity, and, ultimately, the old debate on external and internal factors of structuralist and Marxist theories of dependence to explain the lack of progressive structural change and diversification of the export structure in Latin America.