Earnings Surprise "Materiality" as Measured by Stock Returns

Ranked earnings surprise portfolios formed from First Call files for 1992–97 are used to assess the annual earnings surprise magnitude for an individual firm sufficient to expect a "significant market reaction." We find that, for an individual firm, the maximum probability of a gain from trading on prior knowledge of any surprise magnitude is .622. The lack of probable trading gains is due to the S–shaped surprise/return relation and the large variance of returns for a given magnitude of surprise. In turn, we find that the S–shape is related empirically to the dispersion of analyst forecasts. Thus, factors underlying dispersion differences are related to the importance or "materiality" of earnings surprise as measured by stock returns and explain at least part of the S–shaped surprise/return relation.