中文摘要
我们构建了一个易于处理的赤字与债务动态分析框架。“免费午餐”式财政赤字——即在不提高未来税收的情况下增加支出的赤字——仅当不存在零利率下限（ZLB）约束、且 R < G − φ 时才可持续，其中 φ 为利率对债务水平的敏感度。在存在零利率下限的情形下，过高和过低的赤字都可能导致债务增加，因为后者会削弱需求，并在零利率下限下降低名义增长率。收入不平等的扩大会在零利率下限之外扩大财政空间，但在零利率下限处则会收缩财政空间。通过对模型进行校准，我们发现，2019 年美国实施“免费午餐”政策的空间很小，但日本的政策空间显著更大。(JEL D31, E23, E43, E62, H62, H63)
Abstract
We develop a tractable framework for deficit and debt dynamics. A “free lunch” fiscal deficit—one that raises spending without higher future taxes—is sustainable without zero lower bound (ZLB) only when R < G − φ, where φ is the sensitivity of the interest rate to the debt level. With the ZLB, both high and low deficits can increase debt, as the latter weaken demand and reduce nominal growth at the ZLB. A rise in income inequality expands fiscal space outside the ZLB, but contracts it at the ZLB. Calibrating the model, we find little space for “free lunch” policies for the United States in 2019, but significant space for Japan. (JEL D31, E23, E43, E62, H62, H63)