Bond yields have risen across wealthy nations including Britain, France, Germany, and Japan, while ten-year US Treasury yields climbed above 5 per cent on 14 September for the first time in several years. Ten-year government bond yields across affluent nations have risen to nearly 4 per cent, a level not seen in over 15 years and approximately five times the average recorded between 2015 and 2021.

Borrowing costs are climbing at a time when national debt levels have reached their highest recorded point, with gross public debt in advanced economies representing approximately 110 per cent of GDP, compared with roughly 70 per cent in the early 2000s. Over the same period, the figure more than doubled in the United States and nearly tripled in the United Kingdom, with little public support for spending cuts.

Projections place the fiscal deficit at roughly 6 per cent of GDP for the United States and above 5 per cent for France in the current financial year. For much of the 2010s, low borrowing costs allowed elected officials to set aside concerns about mounting national debt.

Interest rates have been climbing, with the Federal Reserve adjusting its benchmark upward by 0.25 percentage points on September 16. The ECB had acted the previous week, while bond markets were pointing to an end of the low-cost government borrowing environment. Heavily indebted entities may soon face the full weight of elevated borrowing costs as rising interest rates begin to affect their financial obligations.

Historically, administrations have navigated periods of elevated bond yields and periods of elevated debt separately, though rarely both simultaneously within living memory. Back in 2007, when median bond yields across wealthy nations hovered near their current levels, governments were issuing debt equivalent to roughly 11 per cent of GDP. In the current year, they will need to sell more than double that volume of debt — both to cover enlarged budget shortfalls and to refinance bonds originally issued during a period of considerably lower interest rates.

Debt servicing costs now account for over 3 per cent of GDP across OECD member nations, rising to nearly 5 per cent in the United States. A large portion of existing borrowing was locked in at historically low interest rates, and as those obligations come due, repayment costs are expected to rise.

According to projections from the Committee for a Responsible Federal Budget, a non-partisan policy research body, annual debt-servicing expenditure in the United States may climb to around $US2.7 trillion by 2030 — nearly triple what it stands at today — if borrowing rates hold near their current levels. This figure surpasses what the federal government allocates to either Medicare or Social Security, while near-term government bond yields largely track investor expectations about where central bank interest rates are heading.

Over longer time horizons, however, investors tend to place greater weight on inflation risk and the health of public finances. Their exposure to long-duration bonds continued to shrink throughout the period, even as rate cuts were introduced by most central banks across large advanced economies in 2024.

According to OECD projections, the average "term premium" — the additional yield investors require to hold longer-dated debt over shorter-term instruments — is forecast to have climbed by over one percentage point relative to pre-pandemic levels by the close of 2025. The term premium in the United States has continued its upward trajectory throughout the year, reaching levels not seen in over a decade, with mounting uncertainty over the country's fiscal position weighing on the appeal of Treasury bonds.

Historically, market participants accepted reduced returns on US Treasury bonds relative to comparable instruments, given their reputation for stability and ease of trading. Research by Lira Mota of the Massachusetts Institute of Technology, subsequently updated by Hanno Lustig of Stanford University, measures the gap between Treasury bonds and top-rated corporate debt — once default risk is removed — and concludes that the so-called "convenience yield," representing the premium investors sacrifice to hold government securities, had nearly vanished by July of this year.

Losing this advantage carries a notable cost at a time when trillions of dollars are being borrowed through bond markets each year, and several factors point to elevated long-term yields persisting. The multtrillion-dollar expansion of artificial intelligence infrastructure is drawing heavily on private capital, placing it in direct competition with governments for funding from investors.

Concurrently, a number of once-dependable purchasers are withdrawing from the market, with central banks that accumulated government bonds over many years to ward off deflationary pressures now reducing their portfolios. Salary-linked retirement plans backed by long-dated government bonds are being displaced by defined-contribution schemes that channel workers' savings into equities and other higher-risk assets in pursuit of stronger returns — a structural transition that Serdar Celik, who leads the OECD's capital-markets division, describes as having elevated the cost-sensitive investor to the position of marginal price-setter in today's market.

As a result, investors are now seeking higher returns, with governments in 2025 paying roughly two additional percentage points in yield on ten-year bonds compared with the debt they were refinancing. With bond yields remaining elevated, future debt refinancing will carry higher costs, and analysts note that reducing borrowing represents one pathway to easing fiscal pressure, though many policymakers appear inclined toward continued spending.

Trump's wide-ranging tax and spending legislation of 2025 extended the majority of his previous tax reductions on a permanent basis while introducing additional relief measures, with projections estimating the federal deficit would rise by trillions of dollars over the following ten years. Prime Minister Takaichi Sanae has outlined plans to channel government resources into semiconductor and artificial intelligence development alongside a reduction in consumption tax. Controlling government expenditure has proved an ongoing challenge for France as its population grows older and the cost of servicing national debt continues to rise.

Governments have shown a growing tendency to restructure the composition of their debt rather than reduce its overall volume, shifting toward shorter-maturity instruments to sidestep the additional yield demanded by investors for holding longer-term obligations. Longer-dated borrowing now accounts for a smaller portion of total debt issuance than at any point since 2009, with governments increasingly turning to short-term bills that mature within twelve months.

During the 2010s, wealthy nations sold roughly 60 per cent more long-term fixed-rate debt than short-term treasury bills, yet from 2023 onwards the balance has shifted, with bills now representing the greater portion of issuance. Approximately one-quarter of all outstanding US government debt is held in Treasury bills, a proportion that ranks among the highest across developed economies. The aggregate debt burden carries an average maturity of under six years, a figure broadly comparable to levels seen across emerging economies.

Opting for shorter-term debt is not inherently an error, particularly if elevated long-term yields are unlikely to persist over coming decades. Should those pressures endure because underlying appetite for long-dated bonds has weakened structurally — as defined-benefit pension funds contract and central banks pull back from the market — there would be a case for governments to redirect a portion of their debt issuance toward shorter maturities.

Notably, debt repayment schedules are drawing nearer than many governments may have anticipated, with around a third of fixed-rate borrowing across OECD nations due for maturity before 2028 and nearly half set to expire by 2030. Interest rates appear headed upward rather than downward, oil has climbed back above $100 a barrel amid the ongoing conflict in Iran, and diesel prices in the United States have reached a record high. Underlying inflation — which strips out volatile energy and food prices — has held at elevated levels across numerous economies.

The ECB is anticipated to lift borrowing costs at least once more over the coming six months, while futures pricing points to a further quarter-point move from the Fed before March 2027. Nations that are increasingly taking on short-term debt may face a situation where their interest obligations outpace overall economic expansion. Under such conditions, government debt levels could climb even when administrations keep their core budgets — excluding interest obligations — in balance.

Under a scenario where affluent nations roll over their entire debt at current five-year bond rates — using IMF nominal growth forecasts as the baseline — the United Kingdom ranks first among 22 countries analysed, requiring a primary fiscal surplus of around 1.5 per cent of GDP simply to keep its debt-to-GDP ratio from rising. France and Italy face fiscal surplus targets of 1.2 per cent and 1.4 per cent of GDP, respectively.

The United States faces a comparable threshold, set at 1.0 per cent, while a number of other nations retain the capacity to run modest deficits without destabilising their debt levels. Japan, for example, has the capacity to sustain a deficit of 0.8 per cent, given that its economic expansion is projected to exceed the interest rate on its borrowings, whereas the majority of nations currently fall well short of achieving comparable fiscal positions.

According to some analysts, the country's primary deficit stands at close to 4 per cent of GDP, with estimates suggesting that a fiscal adjustment of roughly five percentage points of GDP would be required to stabilise the debt ratio at current borrowing costs. France's fiscal deficit stands at close to 3 per cent of GDP, requiring an adjustment of approximately four percentage points.

The United Kingdom, which faces the steepest fiscal consolidation requirement among the group, has nonetheless reduced its shortfall over the course of the year and incorporated much of that adjustment into its forward budget projections. No equivalent strategy exists in France, and lawmakers there have displayed little appetite for developing one ahead of next year's presidential election. Ongoing budget shortfalls and rising bond yields have placed the country's economic trajectory under notable strain.

Twelve months ago, the fiscal gap facing the United States stood roughly two percentage points narrower than current figures show, while France has also seen its own shortfall grow by nearly one percentage point. For numerous European nations, an already elevated tax burden relative to economic output narrows the available fiscal space for raising additional public revenue without risking broader economic consequences. With government tax receipts already accounting for more than half of GDP, France has limited fiscal space available.

Without reductions in borrowing costs and corresponding policy adjustments by governments, shorter debt maturities may defer financial strain but are unlikely to resolve it entirely. When lower-cost borrowing arrangements reach maturity, interest expenditure is projected to increase, fiscal shortfalls may widen, and the degree of budgetary adjustment required to bring debt levels under control could become more substantial. Prolonged delays in addressing fiscal pressures tend to compound the adjustment required when governments eventually act, while rising yields would further strain the underlying numbers.