Doctoral Dissertation Research in Economics: The Effect of Unionization on the Distribution of Wages

本研究的目的是估计工会化对工资分配的因果效应。衡量工会化对工资影响的一个根本障碍是选择偏差：在有工会的工厂里，工资可能会因为工会代表工人以外的原因而有所不同。工人或工厂特征的差异可能导致工会部门内部和外部工资分配的明显差异，从而混淆了工会化的真正效果。本研究试图通过使用回归不连续（RD）研究设计来克服这些选择问题。在这种情况下，设计的关键特征是，为了让工会代表工厂的工人，大多数工人必须在认证选举中投票支持它。如果工会在选举中险胜的工厂和工人与工会在选举中险败的工厂和工人具有可比性，那么就可以估计工会化对工资分配的影响。本研究采用一种新开发的方法，利用研发设计来估计分配效应。该方法允许工会组织具有异质效应，并允许工会地位的选择效应。通过这种方法得出的估计与工会组织对接近选举份额50%的工厂工资分配的影响是一致的。为了衡量工会化对工人工资分配的影响，该研究使用了美国人口普查局纵向雇主-家庭动态（LEHD）项目中的个人工资数据。就业历史档案（EHF）包含个人的季度收入记录。该项目使用LEHD的单位对工人的估算，将个人工资数据与工厂级NLRB工会认证选举数据合并。长期以来，工会在劳动力市场中的作用及其对工资分配的影响一直是劳动经济学的一个重要话题，尤其是在过去三十年中，因为工会化率的下降可能是导致美国收入分配日益不平等的一个因素。由于可用的计量经济技术，迄今为止的研究往往侧重于平均效应。最近的一些研究（例如，DiNardo和Lee， 2004）引入了准实验方法，包括RD来估计工会对经济结果的因果影响。这是一种克服经典选择偏差的有希望的方法。许多研究也考虑了工会对不平等的影响，但迄今为止还没有一个研究将准实验方法与关注分配效应结合起来。本研究的智力价值在于应用新的计量经济学技术，使用准实验设计来估计工会化的分布效应，并使用大型管理数据集，这些数据集可能提供比许多先前研究中使用的调查数据更好的准确性和统计能力。更广泛的影响：工会组织对工资分配的因果影响对政策和学术界的不平等讨论都很重要。这项研究的广泛影响包括为围绕工会在劳动力市场中的作用的政策辩论提供信息（例如，最近在国会提出的“卡片检查法案”），以及关于制度变革与技能偏向的技术变革相对重要性的学术辩论。另一个更广泛的影响是创建了一个单一的数据集，其中合并了个体工人和工厂的管理数据，这对未来的研究人员很有价值。

The objective of the research is to estimate the causal effect of unionization on the distribution of wages. A fundamental obstacle to measuring the effect of unionization on wages is selection bias: wages within unionized plants may differ for reasons other than the fact that workers there are represented by a union. Differences in either worker or plant characteristics could give rise to an observed difference between the distribution of wages inside and outside of the unionized sector, confounding the true effect of unionization. This study seeks to overcome these selection issues by using a regression discontinuity (RD) research design. The critical feature of the design in this context is that in order for a union to represent workers at a plant, a majority of the workers must vote for it in a certification election. If plants and workers where the union barely won the election are comparable to plants and workers where the union barely lost, then the effect of unionization on the distribution of wages can be estimated. The research implements a newly developed methodology to estimate distributional effects using the RD design. The methodology allows for unionization to have heterogeneous effects, and allows for selection effects in union status. The estimates produced by this methodology are consistent for the effect of unionization on the distribution of wages for plants that were close to the election share cutoff of 50 percent. In order to measure the effect of unionization on the distribution of workers' wages, the research uses individual-level wage data from the U.S. Census Bureau's Longitudinal Employer-Household Dynamics (LEHD) program. The Employment History File (EHF) contains quarterly records of individuals' UI-covered earnings. This project uses the LEHD's Unit-to-Worker imputation to merge individual wage data with plant-level NLRB union certification election data. The role of unions in the labor market and their effect on the distribution of wages have long been an important topic in labor economics, but especially over the past three decades, as the decline in unionization rates may be a contributing factor to the increasing inequality observed in the US income distribution. Research to date has tended to focus on average effects because of available econometric techniques. A number of recent studies (e.g., DiNardo and Lee, 2004) have introduced quasi-experimental methods, including RD to estimate the causal effect of unions on economic outcomes. This is a promising approach to overcome the classical selection bias. Many studies have also considered the effect of unions on inequality, but none to date have combined quasi-experimental methods with a focus on distributional effects. The intellectual merit of this study lies in the application of new econometric techniques to estimate using a quasi-experimental design, the distributional effect of unionization, and in the use of large administrative datasets that are likely to provide better accuracy and statistical power than survey data used in many previous studies.Broader Impacts: The causal effect of unionization on the distribution of wages is important to to discussions of inequality, both in policy and academic circles. The broader impact of the research includes informing policy debates around the role of unions in the labor market (for example, the Card Check Bill recently introduced in Congress), as well as the academic debate about the relative importance of institutional change versus skill-biased technological change. Another broader impact is the creation of a single dataset with merged administrative data on both individual workers and plants which will of value to future researchers.