Sovereign Debt at the Limit: How Advanced Economies Are Running Out of Fiscal Space

From Cheap Debt to Expensive Debt: The Rate Shock

For roughly fifteen years between the 2008 financial crisis and 2022, advanced economy governments borrowed at historically low — and sometimes negative — real interest rates. This created a powerful illusion: debt was not only manageable but almost costless. Governments that borrowed to spend during this period faced little immediate consequence in their debt-servicing budgets. The stock of debt grew steadily, but interest payments as a share of GDP barely moved.

The interest rate rises of 2022–2024 shattered this arithmetic. As central banks lifted rates sharply to fight inflation, the cost of new borrowing rose immediately for short-dated debt. For longer-dated bonds, the repricing was slower — governments had locked in low rates on bonds with ten or thirty year maturities. But as those bonds mature and are rolled over at current rates, the interest bill climbs with each auction. The US Congressional Budget Office now projects interest payments will exceed 3.5% of GDP by 2028 — above the historical average of 2.1% — and continue rising.

Crowding Out: What Debt Service Displaces

The fiscal consequence that matters most is crowding out. Every pound, dollar, or euro spent on interest is a pound, dollar, or euro that cannot be spent on something else without either raising taxes or borrowing more. In the United Kingdom, rising debt interest costs have eaten directly into health service budgets and capital investment allocations. In the United States, the interest bill now exceeds defence spending — a threshold that concentrates minds in Washington. In Italy, the share of government spending consumed by interest payments is approaching 15%.

The crowding-out problem is particularly acute because the demands on government budgets are also rising structurally. Ageing populations require more healthcare and pension spending. Climate adaptation requires investment in flood defences, grid infrastructure, and urban planning. Defence budgets across NATO members are rising toward or beyond 2% of GDP targets. All of these demands compete with debt service for a share of tax revenues that, in most countries, is not growing fast enough to accommodate them all.

What Markets Are Saying

Bond markets are sending a clear but polite signal. The "term premium" — the additional yield investors demand for holding ten or thirty-year government bonds rather than rolling over short-term bills — has turned decisively positive after years of being near zero or negative. In the US, term premium estimates from the Federal Reserve Bank of New York rose above 50 basis points in 2023 and have remained elevated. In the UK, the gilt market delivered a sharper lesson in 2022 when a poorly-received fiscal package caused yields to spike and required Bank of England intervention to stabilise pension funds.

These are not yet signs of crisis — markets still buy government bonds at each auction, and spreads for most advanced economies remain far below the levels seen during the eurozone sovereign debt crisis of 2010–2012. But the direction of travel is clear. Investors are pricing in fiscal uncertainty at the margin, and that pricing shows up directly in the government's borrowing cost on every new bond it issues.

The Path Forward: Consolidation Without Collapse

The IMF's prescription is gradual, credible fiscal consolidation — bringing spending and revenues into better balance over a multi-year horizon, without the kind of sharp austerity that choked recoveries after 2010. This means different things in different countries: in the US, it involves addressing the structural gap between entitlement spending and revenues through some combination of revenue measures and benefit reforms. In Europe, it means enforcing the fiscal rules of the Stability and Growth Pact more consistently than in the past. In Japan, it requires finding a path to primary balance — revenues exceeding non-interest spending — that does not tip the economy back into deflation.