Not necessarily: a firm's fundamental value increases with uncertainty about average future profitability, and this uncertainty was unusually high in the late 1990s. After calibrating a stock valuation model that takes this uncertainty into account, we compute the level of uncertainty that is needed to match the observed Nasdaq valuations at their peak. The uncertainty we obtain seems plausible because it matches not only the high level but also the high volatility of Nasdaq stock prices. In general, we argue that the level and volatility of stock prices are positively linked through firm-specific uncertainty about average future profitability.

ABSTRACT We analyze how changes in government policy affect stock prices. Our general equilibrium model features uncertainty about government policy and a government whose decisions have both economic and noneconomic motives. The model makes numerous empirical predictions. Stock prices should fall at the announcement of a policy change, on average. The price decline should be large if uncertainty about government policy is large, and also if the policy change is preceded by a short or shallow economic downturn. Policy changes should increase volatilities and correlations among stocks. The jump risk premium associated with policy decisions should be positive, on average.