Reaching for Duration

Using historical data on U.S. commercial bank balance sheets, we show that banks’ maturity mismatch has more than tripled since the mid-1980s, moving in close lockstep with declining interest rates and term premia. We rationalize these trends in a model of bank portfolio choice in which banks must cover operating costs out of current earnings. When term premia or short-term rates decline, banks extend the duration of their assets to remain profitable. This “reaching for duration” effect is convex in the degree of term premium compression. The resulting maturity mismatch renders banks increasingly vulnerable to self-fulfilling runs by uninsured depositors. Consistent with the model, less profitable banks subsequently raise their asset maturities, particularly in periods of low term premia and large Federal Reserve asset holdings. Quantitative easing, designed to remove duration risk from the private sector, may thus paradoxically concentrate it on bank balance sheets and undermine financial stability.