Banking stability, reputational rents, and the stock market: should bank regulators care about stock prices?

In this paper I begin with a model that generates quantity credit rationing by banks in the spot credit market when the stock market is not doing well, i.e., asset prices are low. Then I provide a theoretical rationale for a bank loan commitment as partial insurance against such future rationing. Incorporating uncertainty about both the creditworthiness of borrowers and the abilities of banks to screen borrowers, I show that the reputational concerns of banks can lead to an equilibrium in which loan commitments serve their role in increasing the supply of credit relative to the spot credit market, but produce the inefficiency of excessive credit supply when the stock market is doing well. Despite this, welfare is higher with loan commitments than with spot credit. ; I use this result to then examine whether the level of the stock market--and more generally asset prices--should matter to bank regulators. My analysis suggests that it should, but not for the usual reason that a bull stock market could trigger inflation. Rather, it is because reputation-concerned banks lend too much during bull markets, leading to a worsening of credit quality and a higher liability for the federal deposit insurer. More stringent stock market information disclosure rules tend to attenuate this distortion and thus deserve consideration by bank regulators. A regulatory policy implication of the analysis is that regulation should be \\"state-contingent\\"--regulatory auditing of bank asset portfolios should be more stringent during bull stock markets, or asset pricing bubbles.