2014 Essays

Economic Crisis and Share Price Unpredictability: Reasons and Implications

Fox, Edward G.; Fox, Merritt B.; Gilson, Ronald J.

During the recent financial crisis, there was a dramatic spike in “idiosyncratic volatility”—the volatility of individual firm share prices after adjustment for movements in the market as a whole. The average firm’s increase was a remarkable five-fold as measured by variance. This dramatic spike is not peculiar to the most recent crisis. Rather, it has occurred with each major downturn in the economy since the 1920s, as our paper shows for the first time. These spikes present a puzzle in terms of existing economic theory. They also have important implications for several areas of corporate and securities law where the capacity of securities prices to reflect available information is particularly important. Examples include the presumption of reliance, loss causation and materiality in fraud-on-the-market suits, materiality in insider trading cases, and the corporate law regulation of defenses undertaken by targets of hostile takeover attempts. The continuing centrality of these issues is underscored by this week’s decision in Halliburton Co v. Erica P. John Fund, where the Supreme Court ruled that a defendant can defeat a fraud-on-the-market case class certification by showing that the alleged misstatement had no impact on price.