Deposit insurance reduces liquidity risk but can increase insolvency risk by encouraging reckless behavior. Several U.S. states installed deposit insurance laws before the creation of the Federal Deposit Insurance Corporation, and those laws applied only to some depository institutions within those states. These experiments present a unique testing ground for investigating the effect of deposit insurance. We show that deposit insurance removed market discipline constraining uninsured banks. Taking advantage of World War I's rise in world agricultural prices, insured banks increased their insolvency risk and competed aggressively for deposits. When prices fell after the war, the insurance systems collapsed and suffered high losses.

Liquidity shocks transmitted through interbank connections contributed to bank distress during the Great Depression. New data on interbank connections reveal that banks were vulnerable to closures of their correspondents and their respondents. Further, banks were less responsive to network liquidity risk in their management of cash and capital buffers after the Federal Reserve was established, suggesting that banks expected the Fed to reduce that risk. The Fed's presence weakened incentives for the most systemically important banks to maintain capital and cash buffers against liquidity risk, and thereby likely contributed to the banking system's vulnerability to contagion during the Depression.