Identifying the impact of local firm concentration on individual firm performance is likely to produce a selection bias related to the positive effects of local concentration if agglomeration economies and natural advantages coincide. We overcome this problem by exploiting exogenous variation...

We identify the impact of local firm concentration on incumbent performance in a historic setting that has quasi-experimental characteristics. When Germany was divided after World War II, many firms in the machine tool industry fled the Soviet-occupied zone to prevent expropriation. We show that...