中文摘要
过度债务的财政成本应予以动态评估，以反映预期的增长、赤字与利率。通过研究这些变量的联合行为，并在世代交叠和源自社会保障的结构性赤字背景下，我们将政府债务承受能力定义为：在当前财政参数保持不变的情况下，恰好能够一直维持直至某个不稳定稳态的债务水平，在该稳态中，基本赤字将永远持续。低于承受能力时，债务收敛至一个稳定的稳态；超过承受能力时，债务将发散失控。若要超出承受能力而不致失控，就需要未来更高的税收或削减支出，这才是真正的财政成本。引入货币之后，若泰勒系数小于一，承受能力会随目标名义利率的上升而提高。通过补贴创新来提高承受能力颇具挑战，因为其收益很难超过成本。本文由 Lukas Schmid（金融）录用。资助：P. Ehling 感谢挪威奥斯陆高等研究中心（Centre for Advanced Study）的支持，该中心在 2024/25 学年资助并接待了其研究项目（世代交叠下异质投资者的资产定价）。补充材料：在线附录与数据文件可从 https://doi.org/10.1287/mnsc.2024.06528 获取。
Abstract
Fiscal costs of excessive debt should be assessed dynamically reflecting anticipated growth, deficits, and interest rates. Studying their joint behavior, with overlapping generations and structural deficits arising from social security, we define government debt capacity as the level that can be just sustained with current fiscal parameters unchanged all the way to an unstable steady state, in which primary deficits last forever. Below capacity, debt converges to a stable steady state. Above capacity, debt unravels. Exceeding capacity without unraveling requires higher future taxes or reduced expenditures, which is the true fiscal cost. With money, capacity increases with the target nominal interest rate if the Taylor coefficient is below one. Increasing capacity by subsidizing innovation is challenging as benefits hardly surpass costs. This paper was accepted by Lukas Schmid, finance. Funding: P. Ehling acknowledges support of the Centre for Advanced Study in Oslo, Norway, which funded and hosted his research project (Asset Pricing with Heterogeneous Investors in Overlapping Generations) during the 2024/25 academic year. Supplemental Material: The online appendices and data files are available at https://doi.org/10.1287/mnsc.2024.06528 .