Entrepreneurship, small businesses and economic growth in cities
研究创业对城市就业和工资增长的影响，利用1975年州破产法中的宅基地豁免额和地下水层覆盖比例作为工具变量，发现小企业诞生率提高10%会在10年后使都市区就业增长1.3-2.2%，工资增长1.2-2.0%，且效应会溢出到整个城市经济。
Does entrepreneurship cause local employment and wage growth, and if so, how large is the impact? Empirical analysis of such a question is difficult because of the joint determination of entrepreneurship and economic growth. This article uses two different sets of variables—the homestead exemption levels in state bankruptcy laws from 1975 and the share of metropolitan statistical area (MSA) overlaying aquifers—to instrument for entrepreneurship and examine urban employment and wage growth between 1993 and 2002. Despite using different sets of instrumental variables, the ranges of two-stage least squares estimates are surprisingly similar. A 10% increase in the birth of small businesses increases MSA employment by 1.3–2.2%, annual payroll by 2.4–4.0%, and wages by 1.2–2.0% after 10 years. Furthermore, an accounting exercise shows that the employment and payroll growth from entrepreneurship are not confined to the initially created businesses but spillover to the aggregate urban economy.