Do real interest rates reliably measure the welfare cost of government debt?
Core argument: When firms hold market power in neoclassical growth models, the real interest rate sits about 4 percentage points below the net marginal product of capital, suggesting a social return on capital exceeding 8% and dynamic efficiency in the U.S. economy.
In neoclassical growth models, incorporating firm market power reveals that real interest rates are a poor indicator of welfare effects from increased government debt. When firms have market power, the real interest rate is about 4 percentage points below the net marginal product of capital, suggesting a social return on capital exceeding 8%. This indicates dynamic efficiency in the U.S. economy. However, government debt can crowd out capital, reducing aggregate consumption if the net marginal product of capital surpasses the growth rate. The presence of market power complicates the welfare analysis, as the aggregate and generational effects of debt may conflict, unlike in competitive markets. This underscores the inadequacy of using real interest rates alone to assess welfare impacts of government indebtedness.


