Chapter 5. The Empirics of Agglomeration Economies We propose an integrated framework to discuss the empirical literature on the local determinants of agglomeration effects. We start by presenting the theoretical mechanisms that ground individual and aggregate empirical specifications. We gradually introduce static effects dynamic effects and workers’ endogenous location choices. We emphasize the impact of local density on productivity but we also consider many other local determinants supported by theory. Empirical issues are then addressed. The most important concerns are about endogeneity at the local and individual levels the choice of a productivity measure between wages and total factor productivity and the roles of spatial scale firms’ characteristics and functional forms. Estimated impacts of local determinants of productivity employment and firms’ location choices are surveyed for both developed and developing economies. We finally provide a discussion of attempts to identify and quantify specific agglomeration mechanisms.