This paper analyzes optimal asset-purchase policies in a macroeconomic model with banks, which face occasionally-binding balance-sheet constraints. It proves analytically that asset-purchase policies are effective in offsetting large financial disturbances, which impair banks’ capital position. It warns, however, that the policy can remain ineffective after non-financial shocks and might offer no substitute for interest rate policy when the latter is constrained by the lower bound. Furthermore, the asset-purchase policy is addictive because it flattens the yield curve, reduces the profitability of the banking sector, and therefore slows down its recapitalization. Consequently, the optimal exit from large central bank balance sheets is gradual.

本文分析了具有银行的宏观经济模型中的最优资产购买政策，该模型有时会遇到约束资产负债表的约束。从分析上证明，资产购买政策可以有效地抵消大规模的金融动荡，从而扰乱银行的资本状况。但是，它警告说，在非金融冲击之后，该政策可能仍然无效，并且当利率政策受到下限的限制时，它可能无法替代利率政策。此外，资产购买政策令人上瘾，因为它会使收益率曲线变平，降低银行业的盈利能力，从而减慢其资本重组速度。因此，大型中央银行资产负债表的最佳退出是渐进的。