Market Participation and Share Prices

Share prices are analyzed in an overlapping generations model in which the generational size is random. This models stochastic fluctuations of market participants and can explain noninformational volatility of share prices. There exists a (stochastic) stationary equilibrium, which may be nonunique. In equilibrium, (a) the share price increases and (b) expected utility decreases with the generational size. A decline of this size below a critical level induces a crash: the stock price falls substantially, shares are undervalued, and investors' demand is restricted by illiquidity. Further, the model predicts the empirically observed positive correlation between volume of trade and absolute price changes.