Measures of urban productivity are typically positively associated with city population. But is this relationship causal? We discuss the main sources of bias in the proper identification of agglomeration effects. We also assess a variety of solutions that have been proposed in the literature to...

Does productivity increase with density? We revisit the issue using French wage and TFP data. To deal with the ‘endogenous quantity of labour’ bias (i.e., urban agglomeration is consequence of high local productivity rather than a cause), we take an instrumental variable approach and...