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.

ABSTRACT We examine the long‐standing question of whether firms derive value from investment bank relationships by studying how the Lehman collapse affected industrial firms that received underwriting, advisory, analyst, and market‐making services from Lehman. Equity underwriting clients experienced an abnormal return of around −5%, on average, in the 7 days surrounding Lehman's bankruptcy, amounting to $23 billion in aggregate risk‐adjusted losses. Losses were especially severe for companies that had stronger and broader security underwriting relationships with Lehman or were smaller, younger, and more financially constrained. Other client groups were not adversely affected.