Cleaning Up the Kitchen Sink: Growth Empirics When the World Is Not Simple

This paper explores the relevance of unknown nonlinearities for growth empirics. Recent theoretical contributions and case-study evidence suggest that nonlinearities are pervasive in the growth process. I show that the postwar data provide strong evidence in favor of generalized non-linearities. I provide two alternative mechanisms for making inference about the effects of production-function shifters on growth that do not make a priori assumptions about functional form: monotonicity tests and average derivative estimation. The results of these tests point towards a greater role for structural variables and a smaller role for policy variables than the linear model.