We quantify the gains from regulating maturity transformation in a model of banks that finance long-term assets with nontradable debt. Banks choose the amount and maturity of their debt by trading off investors’ preferences for short maturities with the risk of systemic crises. Pecuniary externalities make unregulated debt maturities inefficiently short. In calibrating the model to eurozone banking data for 2006, we find that lengthening the average maturity of wholesale debt from 2.8 to 3.3 months would produce welfare gains with a present value of euro 105 billion, while the lengthening induced by the NSFR would be too drastic. Received November 27, 2014; editorial decision November 14, 2016 by Editor Itay Goldstein.

We quantify the gains from regulating maturity transformation in a model of banks that finance long-term assets with nontradable debt. Banks choose the amount and maturity of their debt by trading off investors’preferences for short maturities with the risk of systemic crises. Pecuniary externalities make unregulated debt maturities inefficiently short. In calibrating the model to eurozone banking data for 2006, we find that lengthening the average maturity of wholesale debt from 2.8 to 3.3 months would produce welfare gains with a present value of euro 105 billion, while the lengthening induced by the NSFR would be too drastic.

We model the debt maturity choice of firms in the presence of fixed issuance costs in the primary market and search frictions in the secondary market for debt. In the secondary market, short maturities improve the bargaining position of sellers, which reduces the required issuance yield. Long maturities reduce reissuance costs. The optimally chosen maturity trades off both considerations. Equilibrium exhibits inefficiently short maturity choices. An individual firm does not internalize that a longer maturity increases expected gains from trade in the secondary market, which attracts more buyers and, hence, facilitates the sale of debt issued by other firms.