Productivity Dispersion, Between-Firm Competition, and the Labor Share

I study the effect of labor market imperfections on the labor share in a tractable model that emphasizes the interaction between productivity dispersion and firm competition for workers. I calibrate the model using administrative data covering the universe of firms in Canada from 2000 to 2015. As in the data, most firms have a high labor share, yet the aggregate labor share is low due to the disproportionate effect of a small fraction of large, highly productive firms. I find that a rise in the dispersion of firm productivity causes the aggregate labor share to decline in favor of firm profits. The mechanism is that productivity dispersion effectively shields high-productivity firms from wage competition. Regression evidence from cross-country and cross-industry data supports both the model prediction and mechanism.