Unexpected Media Coverage and Stock Market Outcomes: Evidence from Chemical Disasters∗

Using the event-study methodology and multivariate regressions, this paper examines the intensity of media coverage, its determinants and its marginal effect on stock returns following chemical disasters. To do this, we build an original dataset of chemical explosions that occurred worldwide from 1990-2005. First, our results show that news coverage increases with the social and environmental consequences of the accident. Second, to deal with the fact that news coverage is determined simultaneously with stock returns, we suggest two valid and original instrumental variables: a measure of the firm’s newsworthiness and a measure of daily news pressure at the time of the disaster. We find that unexpected news coverage due to chemical disasters also respond to these conjunctural factors, and is truly exogenous to abnormal returns. Third, we show that, all else being equal (pollution, number of casualties, and firm profile), the stock market reaction to intense press coverage is delayed, and becomes negative in the long-term. At the same time, there is clear evidence that in the first days news coverage mitigates the market value losses. We interpret these results as evidence that investors are slow to recognize the extent of the loss associated with the public implications of news coverage (e.g., image and public trust deterioration). In addition, in contrast to previous studies, we argue that press coverage is not necessarily associated with increased investor attention. Classification code: G12, G14, G30, M30.