According to Verdoorn’s law, productivity growth is endogenous to output growth, due to the existence of increasing returns to scale, broadly defined. Such an idea is at the root of both the endogenous growth theory and the Kaldorian approach. While in Kaldor’s view, a country’s growth is demand-driven, in the endogenous growth theory, growth is determined by the growth of the factors of production and hence growth is supply-constrained. This article empirically tests both assumptions for Verdoorn’s law by using a dynamic panel of manufacturing industries for seventy countries at different stages of development for the years between 1963 and 2009. In order to distinguish between these approaches, two different specifications are estimated where the growth of output and the supply of factors of production are instrumentalized by system generalized method of moments (GMM)estimators. The results show that, if it is assumed that the growth rates of countries are demand-driven, a faster growth of output increases productivity growth due to the existence of increasing returns. Alternatively, if it is assumed that output growth is driven by the growth of the supply of the factors of production, it is not possible to conclude that productivity growth is induced by output growth.