A major empirical challenge in economics is to identify how regulations (such as labor protection) affect economic efficiency. Almost all countries have regulations that increase costs when firms cross a discrete size threshold. We show how these size-contingent regulations can be used to identify the equilibrium and welfare effects of regulation through combining a new model with the joint firm-level distribution of size and productivity. Our framework adapts the Lucas (1978) model to a world with size-contingent regulations and applies this to France where there are sharp increases in firing costs (which we model as a labor tax) when firms employ 50 or more workers.

Using administrative data on the population of firms 2002 through 2007, we show how this regulation has major effects on the distribution of firm size (a “broken power law”) and productivity. We then econometrically recover the key parameters of the model in order to estimate the costs of regulation which appear to be non-trivial.