Firm Growth Through New Establishments

This paper analyzes the distribution and growth of firm-level employment along two margins: the extensive margin (the number of establishments in a firm) and the intensive margin (the number of workers per establishment in a firm). We utilize administrative datasets to document the behavior of these two margins in relation to changes in the U.S. firm-size distribution. In the cross section, we find the firm-size distribution, as well as both extensive and intensive margins, exhibits a fat tail. The increase in average firm size between 1990 and 2014 is primarily driven by an expansion along the extensive margin, particularly in very large firms. We develop a tractable general-equilibrium growth model with two types of innovations: external and internal. External innovation leads to the extensive margin of firm growth, and internal innovation leads to intensive-margin growth. The model generates fat-tailed distributions in firm size, establishment size, and the number of establishments per firm. We estimate the model to uncover the fundamental forces that caused the distributional changes from 1995 to 2014. The largest contributors to the increase in the number of establishments per firm are the external innovation cost and the decline in establishment exit rate