财政赤字的适度理论

American Economic Review · 2025 · [{"name": "Atif Mian", "affiliation": ["Princeton University"]}, {"name": "Ludwig Straub", "affiliation": ["Dana-Farber/Harvard Cancer Center"]}, {"name": "Amir Sufi", "affiliation": []}]

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。一种“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——在不存在零利率下限（ZLB）的情况下，只有当 R < G − φ 时才具有可持续性，其中 φ 为利率对债务水平的敏感度。在存在 ZLB 的情况下，高赤字和低赤字均可能增加债务，因为后者会削弱需求并降低 ZLB 下的名义增长。收入不平等上升会在 ZLB 之外扩大财政空间，但在 ZLB 下收缩这一空间。通过校准模型，我们发现 2019 年美国几乎没有实施“免费午餐”政策的空间，但日本具有显著空间。（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)