Recent work by Diether, Malloy, and Scherbina (2002) has established a negative relationship between stock returns and the dispersion of analysts' earnings forecasts. I offer a simple explanation for this phenomenon based on the interpretation of dispersion as a proxy for unpriced information risk arising when asset values are unobservable. The relationship then follows from a general options‐pricing result: For a levered firm, expected returns should always decrease with the level of idiosyncratic asset risk. This story is formalized with a straightforward model. Reasonable parameter values produce large effects, and the theory's main empirical prediction is supported in cross‐sectional tests.

Momentum effects in stock returns need not imply investor irrationality, heterogeneous information, or market frictions. A simple, single‐firm model with a standard pricing kernel can produce such effects when expected dividend growth rates vary over time. An enhanced model, under which persistent growth rate shocks occur episodically, can match many of the features documented by the empirical research. The same basic mechanism could potentially account for underreaction anomalies in general.