Market Sector Reactions To 9-11: An Event Study

This study presents an overview of how stocks believed to be most vulnerable to the 9-11 attacks reacted, in particular, in the pre-event period. The insider information theory about pre-knowledge of the attacks is carefully analyzed in both the airlines and the financial services sectors of the market. Standard event study methodologies are used to calculate abnormal returns before and after the attacks. Also, riskadjusted returns are examined to determine whether investors achieved differential performance during the event period. Expectedly, significant negative excess returns occurred in the airlines and financial services sectors due to the incident. A subsequent reversal of excess returns indicates that markets may have overreacted to the attacks. Uncertainties in energy supply resulted in high but short-lived oil prices. Pre-event negative excess returns in airlines and financial stocks are suggestive of a trading pattern that may have been driven by expectation of an impending anomaly.