How much will government interest costs rise across advanced economies?
Core argument: The authors estimate interest spending on marketable debt will rise by an average of 0.5pts of GDP across G10 economies by 2029, based on the current forward curve, projected deficit paths, and existing weighted average maturities.
To project future government interest costs, we build a model based on future interest rate curves, the path for future deficits, and the term structure of future debt issuance. Using the current forward curve, projected deficit paths, and existing WAMs, we can estimate a baseline rise in interest rate costs over time. Using this model we estimate that interest rate spending on marketable debt will rise across G10 economies on average by 0.5pp of GDP by 2029. Although the increase varies, we estimate countries such as France, Japan, and the United States will face the largest increases in higher interest costs given the future path for deficits, debt, and the current forward curve. We observe that reducing the policy rate has a stronger impact on reducing the increase in interest costs in the US where a 100bp of additional cut could reduce the interest cost increase by 0.51pp of GDP. The US had the lowest sensitivity to a change in WAM: adding just an additional cut would have a stronger effect than actively reducing the WAM by 2 years. Combining these measures would result in a bigger saving.



