Long-Run Impacts of Unions on Firms: New Evidence from Financial Markets, 1961–1999 *
利用1961-1999年美国私营企业工会选举数据与股票市场数据，发现工会化使企业股权价值平均每名工会工人减少40,500美元，该影响在工会化后15-18个月才完全显现，短期事件研究无法检测。
We estimate the effect of new private-sector unionization on publicly traded firms' equity value in the United States over the 1961--1999 period using a newly assembled sample of National Labor Relations Board (NLRB) representation elections matched to stock market data. Event-study estimates show an average union effect on the equity value of the firm equivalent to $40, 500 per unionized worker, an effect that takes 15 to 18 months after unionization to fully materialize, and one that could not be detected by a short-run event study. At the same time, point estimates from a regression discontinuity design--comparing the stock market impact of close union election wins to close losses--are considerably smaller and close to zero. We find a negative relationship between the cumulative abnormal returns and the vote share in support of the union, allowing us to reconcile these seemingly contradictory findings. Copyright 2012, Oxford University Press.