Identifying the Heterogeneous Impact of Highly Anticipated Events: Evidence from the Tax Cuts and Jobs Act

Abstract

We develop a method for estimating the stock market impact of aggregate events. Based on using data on both stock and options prices, our technique accounts for two important sources of bias present in traditional methods. First, our method takes into account market anticipation, without the need for information on specific firm characteristics. Many event studies only measure a fraction of an event's full value effect, so the measured market reaction at event resolution can be misleading, particularly in the case of a very high degree of market anticipation. Second, our method is robust to the possibility of the event being good news for some firms and bad for others, without prior specification of this heterogeneity. We apply the method to the passage of the Tax Cuts and Jobs Act (TCJA), which exhibits both anticipation and heterogeneity. We estimate the market anticipated the probability of passage to be as high as 95% 30 days before the event. The full value impact of the TCJA is found to be 12.36%, compared to 0.68% when market anticipation is ignored. The firm-level impact of the TCJA is considerably heterogeneous, with large and innovative firms with high growth prospects being the largest winners.