IMF-当r＜g时公共债务成本增加（英）-2024.1-29页_1mb

Costly Increases in Public Debt when r < g

Summary

This paper examines the macroeconomic costs of increasing public debt in the context where the real interest rate (r) is less than the GDP growth rate (g). Using a general equilibrium overlapping generations (OLG) model with two assets—government debt and private capital—the study demonstrates that even in a low-interest-rate environment where Blanchard argues debt may pose minimal fiscal costs, public debt can still have substantial negative effects.

Key Findings:

1. Crowding-Out Effect: When public debt increases, it crowds out private capital, reducing long-term output. This occurs because government debt competes with private investments, even though the debt’s return is lower than that of private capital.
2. Quantitative Impact: In the U.S., a permanent increase in public debt from 60% to 120% of GDP reduces long-term GDP by approximately 8%. Foreign ownership of debt (30%) reduces this impact to a 4% GDP decline.
3. Mechanism: The crowding-out effect stems from the necessity to allocate a larger share of wealth to government bonds, leading to reduced private capital accumulation and lower output.
4. Robustness: The results hold even when accounting for foreign ownership of debt and alternative financing mechanisms, such as tax adjustments versus debt issuance.

Conclusion: Despite low interest rates, rising public debt imposes significant macroeconomic costs through private capital crowding-out. Policymakers must consider these effects, especially given the endogeneity of r and g.