The information content of security prices

The study derives a relationship between prices changes and earnings changes by expanding the information upon which earnings expectations are conditioned to include data other than prior earnings history. In particular, price is used as a surrogate for additional information available to market participants. This relationship provides an interpretation of the contemporaneous association between price changes and earnings changes previously observed by Ball and Brown (1968) and Beaver, Clarke and Wright (1979), among others. It also provides a basis for inferring from prices the earnings process and the expected future earnings as perceived by market participants. In doing so, it inverts the familiar price-earnings relationship and uses price as a predictor of earnings. The study differs from previous research which has examined the time series behavior of earnings based solely on previous earnings realizations. This approach can potentially lead to earnings forecasting models that are more accurate than the random walk with a drift that has been robust against challengers. In particular, the evidence indicates that security prices behave as if earnings are perceived to be dramatically different from a simple random walk process. Preliminary evidence also indicates that price-based forecasting models are more accurate than the random walk with a drift model.