This study documents empirical anomalies which suggest that either the simple one-period capital asset pricing model (CAPM) is misspecified or that capital markets are inefficient. In particular, portfolios based on firm size or earnings/price (E/P) ratios experience average returns systematically different from those predicted by the CAPM. Furthermore, the ‘abnormal’ returns persist for at least two years. This persistence reduces the likelihood that these results are being generated by a market inefficiency. Rather, the evidence seems to indicate that the equilibrium pricing model is misspecified. However, the data also reveals that an E/P effect does not emerge after returns are controlled for the firm size effect; the firm size effect largely subsumes the E/P effect. Thus, while the E/P anomaly and value anomaly exist when each variable is considered separately, the two anomalies seem to be related to the same set of missing factors, and these factors appear to be more closely associated with firm size than E/P ratios.

The paper examines the optimal behavior of a single dealer who is faced with a stochastic demand to trade (modeled by a continuous time Poisson jump process) and facing return risk on his stock and on the rest of his portfolio (modeled by diffusion processes). Using stochastic dynamic programming, we derive the optimal bid and ask prices that maximize the dealer's expected utility of terminal wealth as a function of the state in which he finds himself. The relationship of the bid and ask prices to inventory of the dealer, instantaneous variance of return, stochastic arrival of transactions and other variables is examined.