Employment Decline During the Great Recession: the Role of Firm Size Distribution
研究发现，大衰退期间本地劳动力市场越集中（由赫芬达尔指数衡量），就业损失越大。通过构建异质性企业模型和实证检验，揭示了企业规模分布通过放大负面冲击、削弱正面冲击来影响就业再分配的机制。
Abstract Over 8,000,000 jobs were lost in the Great Recession, creating widespread economic hardship. This paper documents a novel and robust empirical regularity that highly concentrated local labour markets experienced larger employment declines during the Great Recession. Through setting up a model with heterogeneous firms facing idiosyncratic productivity shocks, I show that firm size distribution summarised by the Herfindahl-Hirschman index plays a crucial role in the reallocation of workers, and it magnifies negative idiosyncratic shocks and attenuates positive ones. I undertake a series of empirical tests to rule out alternative explanations, and show that large employment losses in concentrated labour markets are not driven by highly concentrated industry locations being hit harder during the Great Recession, having smaller labour markets or higher firm leverage ratios. The effect of concentration level is larger in sectors with higher labour supply elasticity, or a higher variance of productivity shocks, and rises during the Great Recession compared to other periods, consistent with my model’s predictions.