When economic activity is concentrated over space or over time, it is more efficient. Most production occurs in geographic hot spots, and most production occurs between 9 and 12 in the morning and 1 to 5 in the afternoon on weekdays. The thick-market efficiencies that encourage the concentration...

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...