Collaborative Proposal: Understanding the City Size Wage Gap

2000年，在人口超过250万的大都市地区，壮年男性的时薪比人口不足10万的地区高31%。此外，在整个都市圈规模范围内，每增加10万人口，工资与人口之间的关系单调增加约1个百分点。这种单调关系对于年龄、学校教育和劳动力市场经验的控制是稳健的。城市规模工资差距的存在意味着，大城市的工人生产率更高。否则，大城市的公司就会迁移到成本更低的地方。这个研究项目将提高我们对城市规模、工资和生产率差距的原因的理解。研究人员开发了一个劳动力市场搜索模型，该模型包含了大城市和小城市之间的内生迁移。当使用纵向数据进行结构估计时，该模型足够丰富，可以根据城市规模恢复工人的潜在能力分布，根据能力和地点获得工作机会的到达率，以及根据能力和地点获得经验的回报。这些估计有助于对城市规模工资差距进行更完整的实证分解，而不是使用现有研究的结果。这一研究路线还提供了新的经验证据，证明大城市生产力更高的各种机制的相对重要性。虽然已有各种关于城市规模工资和生产率差距的研究发现，工资增长率和能力排序的差异作为城市规模的函数是重要的，但仍然缺乏对劳动力市场搜索外部性在产生这些生产率差距方面所起作用的理解。此外，现有的研究主要集中在一次估计一种外部性对生产率的因果影响。很少有人研究各种解释之间潜在的重要相互作用。主要原因是，现有研究中常用的大多数基于回归的程序无法解释居住在大城市的人可能具有使他们更有生产力的未观察到的属性的可能性，而这种未观察到的能力可能与其他因素（如劳动力市场搜索技术）相互作用。随着城市和工作岗位之间的自由流动，外生变异极难发现。因此，拟议的研究通过利用一个模型来帮助确定没有外生变化的城市规模生产力差距的组成部分，从而补充了现有文献。此外，模型的估计可用于执行现有文献中无法实现的分解。更广泛的影响：更好地理解为什么大城市的生产力更高，将极大地帮助我们理解推动社区成功或衰落的重要因素。该研究项目还训练研究生在数据集的仔细构建和现代建模、计量经济学和计算技术的使用方面。

In 2000, hourly wages of prime-age men were 31 percent higher in metropolitan areas of over 2.5 million people than those of less than 100 thousand people. Moreover, the relationship between wages and population was monotonically increasing by about 1 percentage point for each additional 100 thousand in population over the full range of metropolitan area size. This monotonic relationship is robust to controls for age, schooling and labor market experience. The existence of this city size wage gap implies that workers are more productive in larger cities. Otherwise, firms in large cities would migrate to locations with lower costs. This research program would improve our understanding of the causes of the city size wage and productivity gaps. The investigators develop a labor market search model that incorporates endogenous migration between large and small cities. This model is sufficiently rich to allow for recovery of the underlying ability distributions of workers by city size, arrival rates of job offers by ability and location, and returns to experience by ability and location, when structurally estimated using longitudinal data. These estimates facilitate a more complete empirical decomposition of the city size wage gap than is possible using results in existing research. This line of research also produces new empirical evidence on the relative importance of various mechanisms by which larger cities are more productive. While there exists a variety of existing research on the city size wage and productivity gaps finding that differences in wage growth rates and ability sorting as functions of city size are important, there still exists a lack of understanding of the role played by labor market search externalities in particular to generate these productivity gaps. Moreover, existing research largely focuses on estimating causal effects on productivity of one type of externality at a time. Little work has examined the potentially important interaction between various explanations. The main reason is that most of the regression-based procedures commonly used in existing research cannot account for the possibility that those who live in larger cities may have unobserved attributes that make them more productive, and this unobserved ability may interact with the other factors such as the labor market search technology. With free migration between cities and jobs, exogenous variation is extremely difficult to find. The proposed research thus complements the existing literature by making use of a model to help identify components of the city size productivity gap for which there is no exogenous variation. In addition, estimation of the model can be used to perform decompositions that are not possible with results in the existing literature. Broader Impacts: A better understanding of why bigger cities are more productive will greatly inform our understanding the important factors that drive the success or decline of communities. This research program also trains graduate students in the careful construction of data sets and the use of modern modeling, econometric and computational techniques.