Firm size and the Macroeconomy

This dissertation collects two essays on firm size dynamics and aggregate shocks. By employing a model with heterogeneous firms, search frictions and endogenous entry/exit we investigate the business cycle dynamics of the firm size distribution by looking at entry cost and technology shocks. The thesis is divided into two chapters.\\ The first chapter explores how an increase in entry costs affects the size of new entrants and the concentration of employment according to firm size, along with its effects on macro-variables such as unemployment and the exit rate. To this aim we use a BVAR model to estimate the response of such variables to an entry cost shock, then we develop a heterogeneous-firm model with search frictions and endogenous entry/exit dynamics calibrated on data from Business Dynamics Statistics (BDS) database to address our empirical results.\\ We find that positive entry cost shocks increase the average size of entrants and move employment shares toward the largest firms. These results reveal the role of entry costs' fluctuations in explaining the dynamics at business cycle horizons of both firm and employment share distributions according to size.\\ The second chapter perturbed the model with a technology shock to replicate the long-run differential of job destruction due to exit between small and large firms and its empirical response to technology shocks (estimated by a BVAR). Contrary to frameworks with \textit{exogenous} exit, the model is able to account for the volatility of exit and the differential of job destruction due to exit between small and large firms conditional to the technology shock. Moreover we find that not only entry but also exit is a viable amplification channel for the response of unemployment to the shock.\\

La tesi è formata da due capitoli su dinamica della distribuzione delle imprese e shock aggregati. Usando un modello ad imprese eterogenee, la tesi studia le fluttuazioni di ciclo economico dovute a shock alla tecnologia ed ai costi in entrata.