From a theoretical and empirical standpoint, the contribution of infrastructure capital to aggregate productivity and output has been extensively researched. Public capital has been modeled as an additional input in Ramsey-type exogenous growth models and in endogenous models as well. On the empirical front, the literature has witnessed a proliferation of research over the last 20 years following Aschauer’s (1989) seminal paper on the effects of public infrastructure capital on US total factor productivity. His finding of excessively high returns to infrastructure, however, has not held up. Subsequent research using a large variety of data and more robust econometric techniques has yielded widely contrasting empirical results. For instance, Bom and Ligthart (2008) find that estimates of the output elasticity of public capital range from -0.175 to +0.917 in a wide set of empirical research for industrial countries.