We estimate the effect of new unionization on firms’ equity value 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 eq uivalent to a cost of at
least $40,500 per unionized worker. 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. Using the magnitudes from the analysis,
we calibrate a structural “median voter” model of endogenous union determination in order to conduct
counterfactual policy simulations of policies that would marginally increase the ease of unionization.