We empirically document two adjustment margins that are usually absent from the predominant "bank balance sheet lending" view of financial intermediation. For the shadow bank substitution margin, shadow banks substitute for traditional banks among loans that are easily sold. For the balance sheet retention margin, banks switch between balance sheet lending and selling loans based on their balance sheet strength. Estimates from a structural model show that these margins significantly shape policy responses, dampening the effect of capital requirements on lending whose costs are borne by wealthier borrowers. Secondary-market disruptions such as quantitative easing have significantly larger impacts on lending than capital requirements.
