As is well known, banks have liquid liabilities against potentially illiquid assets. Normally, such a “maturity mismatch” does not affect financial stability, as it is unlikely that all depositors would request their money back exactly at the same moment. Yet, when a wider lack of trust occurs a run could follow by menacing the very financial stability, possibly with a serious impact on capital formation and, in the end, on economic growth. Such a problem was particularly apparent up to the first decades of the last century, when financial systems were loosely regulated and central banks were rather reluctant to intervene during liquidity crises as they were tied up by gold standard constraints. In the 1930s, as the financial crisis hit har...