Banking crises are recurrent phenomena that often trigger deep and long-lasting recessions with enormous economic and political costs. Yet the empirical evidence is now overwhelming that banking crises do not come as bolts from the blue – they come after periods of strong bank credit growth and risk-taking, often associated with real-estate bubbles. The crisis of 2008 was no different: it is clear that banks took on more and more risk as bubbles swelled in many countries.

A key research question is why banks take such excessive risks. Many defenders of finance in the recent crisis suggest that the giant institutions were really taken by surprise when the bubble popped. Otherwise, runs the argument, why wouldn’t they have sold off all the junk? The implication of this “behavioral” view is that banks take on high risks because, for example, they neglect unlikely tail risks and have over-optimistic beliefs about the economy.

But there is another, less innocent answer: explicit and implicit bank guarantees by states, such as deposit insurance, provision of central bank liquidity, and bail-outs make it rational for banks to take on excessive risk. Sometimes this “moral hazard” point of view is combined with an “agency failure” account, which stresses how bank managements can escape from control of their shareowners and holders of bank debt.

These views of why banks take on excessive risk are testable. In a recent paper we tackle this question by providing sector-wide evidence from US. We examine what bank insiders were doing before the crisis and use executives’ trading with their own bank shares as a proxy for their understanding of risk before the crisis hit in 2007-08. Specifically, we investigate the relationship between bank’s performance in the crisis and bank executives’ sale of their own bank shares in the period prior to the crisis.

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Copy of the report here…