Argentina’s economic and institutional decline has long posed a conundrum to economists and social scientists. In particular, it challenges theories that seek to explain cross-country growth differences over time. Those theories that claim that institutions have a first-order effect on growth cannot explain the persistent economic decadence of a country that in 1930 was among the most institutionally advanced in Latin America. Theories that claim that that education and growth precede inclusive institutions face a similar problem, since Argentina was one of the most educationally advanced countries in Latin America. The same can be said of theories that claim that social capital is the determinant factor that explains long-term growth. This paper emphasizes the key role played by recurrent cycles of populism in pushing the country into secular decadence and posits that, in Argentina, rising commodity prices have driven the cycles of populism.