Public debts have soared among advanced economies, with the US leading the way. Their sustainability is now a big risk and casts strong headwinds on economic growth.
The repercussions are already being felt in the sovereign bond markets, including in the safest of assets, the impregnable US Treasury markets.
The response, especially the recent actions of the US Treasury, arguably even encroaching into the Fed’s domain, to prevent bond yields from rising are extraordinary. It first announced a temporary swap of the Bank of Japan’s Treasury holdings for dollar cash to pre-empt any liquidation to generate the dollars required to prop up the Yen, and followed up with an announcement to double the purchases of Treasury bonds. More are likely to follow in the months ahead, especially with a President who has announced his intent to wage war against the bond markets.
Chris Giles has an excellent description of America’s ongoing debt surge.
The most relevant measure of US federal government debt, that held by the public, has risen from $3.4tn in 2000 to $32.3tn now, or a rise from 33.7 per cent to more than 100 per cent of GDP in just over 25 years. More importantly, the burden of servicing that debt has doubled, from 11 per cent of tax revenues in 2000 to 21.5 per cent in the first 10 months of the current fiscal year… With the US on a path to continue running deficits close to 6 per cent a year, even at full employment, the debt-to-GDP ratio is set to rise every year, increasing the call on tax revenues to service that debt and the pressure on the Fed to lower interest rates…
Since 2000, when the federal government ran a surplus of 2.3 per cent of national income, primary public spending (excluding net debt interest) has risen from 15.5 to 19.9 per cent of GDP. All of this increase can be accounted for by spending on services for an ageing population — social security, Medicare and veterans’ programmes. On the tax side, revenues have fallen from 20 per cent to 17.2 per cent of GDP over the same period, partly a result of a cyclical peak in revenues at the end of the last millennium and partly the result of tax cuts. First came the Bush tax cuts, which were made permanent on a mostly bipartisan basis during the Obama administration, and then came the 2017 Trump tax cuts… It does not need to eliminate the deficit, but does need to put debt back on a downward path, which almost certainly requires a balanced primary deficit — a metric that excludes net interest costs — something the US has not achieved since 2007 and not on a sustained basis since the 1990s.
The combined debt held by the public and federal agencies in the US now touches $36 trillion. The US interest bill has doubled to more than 3% since 2021, and the fiscal deficit is running at nearly 6% of GDP with little prospect of declining anytime soon.
America does not stand alone. Since the Second World War, as welfare states took hold, public spending as a share of GDP has risen steeply across the developed countries. Further, since the seventies, public debt as a share of GDP has been on a similar upward trend.
Welfare spending has been rising, and subsidy policies have ratcheted up since the global financial crisis.
This increase in public spending and borrowings is a political choice made in response to rising expectations from governments among the electorate.
For measure, in the US, net positive mentions of government support — covering welfare and protectionism — in Democratic and Republican party manifestos have trended higher since the early 1970s, based on calculations from the Manifesto Project’s database. In particular, these mentions have surged since the GFC. This suggests politicians are increasingly pitching policies that extend state assistance to appeal to voters. In the UK, the National Centre of Social Research reported in 2023 that expectations for government to keep prices under control, reduce income differences and provide industry with the help it needs to grow all reached a record, based on the British Social Attitudes survey. Indeed, curbing support hasn’t been easy for governments either. Britain’s Labour party was forced to reverse over £5bn of planned cuts to welfare spending. French politicians are also struggling to agree on how to cut expenditure, given the inevitable pains on the public.
A similar expectation cycle has been set off in the financial markets on monetary policy under the watch of technocratic central bankers like Ben Bernanke and Mario Draghi. These cycles have come to reinforce each other.
A May 2024 paper by John Cochrane and Amit Seru, senior fellows at the Hoover Institution, concurs. It argues that the expectation of central bank support whenever conditions deteriorate inflates stock prices, fuels leverage and, in turn, raises risks of a self-reinforcing monetary policy intervention and taxpayer-funded bailouts. Central banks have also been cautious about unwinding their QE holdings too quickly, fearing market convulsions. This has left their balance sheets elevated, creating a structurally higher liquidity base in the financial system that props up valuations and market activity today.
The rising indebtedness has close historic parallels. In an FT interview, Thomas Piketty pointed to the experiences of European countries in the 19th and 20th centuries.
We have a long history of public debt in France and Britain. Britain had more than 200 per cent of GDP of public debt in the 19th century. In the case of France . . . after each of the world wars, it was between 200 per cent and 300 per cent. The good news is that we’ve always found ways to get rid of it, and in each of the three instances I’m referring to, through different mechanisms, it went down to very little — less than 20 or 30 per cent GDP in a few years. It was never repaid, in effect, as opposed to the British solution in the 19th century, where it took basically one century of budget surplus between 1820 and 1914 to reduce the public debt coming from the Napoleonic War period…
The British approach of the 19th century corresponded with a very aristocratic political system where basically one tier was in power and they wanted taxpayers to reimburse them. Was it the best way to prepare the country for the 20th century? I’m not completely sure, because in effect there was more money put into interest payments than money invested in education. And Britain lagging behind in education with respect to the US or even with respect to Germany or France in the 20th century is the number one explanation for a British decline. I would not recommend doing the same in the future… The most successful experience with large public debt is probably Germany after [the] second world war, where they had this exceptional tax on private wealth which raises a lot of money. This contributes a lot to the reduction of the public debt without any inflation. Of course they were traumatised by inflation in the 1920s, so they didn’t want inflation anymore. The other way, of course, is through inflation, which is a wealth tax on the poor, typically.
A major reason for the surging debt stock since the turn of the millennium has been external wars. It has been estimated that the total cost and future obligations of the post-9/11 wars are about $8 trillion in 2021 dollars, excluding future interest costs on the debt. To put all this in perspective, “the US defence budget in 2025 was over $900bn, equivalent to 35 per cent of total global defence spending and more than three times the defence budget of China, the next most powerful military actor.”
Despite this, the dollar has continued to hold reasonably steady. The exorbitant privilege has ensured the dollar's status as the world's pre-eminent reserve currency and the Treasury market's role as the world's safest haven asset, thereby allowing the US access to unlimited global capital at a low cost. While there are no competitors to the dollar on the horizon, the Treasury's safe-haven status is facing competition.
For one, the central banks, which accumulated reserves by buying up 63% of the extra debt issued by G-7 governments in 2008-21, are now unwinding their balance sheets by running down the dollar component of their reserves. They are instead pursuing alternatives like gold, commodities and the more liquid currencies of smaller developed countries like Switzerland. As William White has pointed out, this has created vulnerabilities.
Indeed, a report by the European Central Bank showed this week that gold had now replaced US Treasuries as the world’s top reserve asset. By the end of last year bullion accounted for 27 per cent of all global central bank reserve assets, up from 20 per cent a year before. Treasuries fell from 25 to 22 per cent over the same time. This leaves a gap that has been substantially filled by hedge funds, mainly American owned but often counted as foreign investors because of their bases in tax havens such as the Cayman Islands. Many own Treasuries as part of highly leveraged “relative value trades”, financed by short-term borrowing that has to be constantly rolled over.
William White, former chief economist of the Bank for International Settlements, points out that this works well — until it does not. White argues that the purchase of government debt by non-bank institutions such as hedge funds depends in turn on their access to short-term financing such as the repo market. He adds: “Should any disturbance interrupt that access, as in March 2020 [during the Covid-19 pandemic] or April 2025 [when Trump announced swingeing tariffs], an intense deleveraging spiral could easily follow.” Recent shocks from hedge fund margin and collateral calls have made the Treasury market more fragile and a potential source of systemic risk.
And there’s more.
White also worries about fiscal dominance — a phenomenon in which the central bank cannot raise interest rates to meet its inflation target because of the punishing servicing cost of high, short-term public debt. This in turn undermines price stability. Another possible concern is financial repression, where the government forces banks and other financial institutions to buy its IOUs at below-market interest rates.
And with bond yields rising, the debt service costs are increasing. One estimate puts an additional $34 bn in financing costs by the end of the first quarter of next year for G7 nations. And this will only rise.
Debt reduction can be achieved, as has happened in the post-war era in the UK, France, the US, etc., and more recently in Greece (more on it later).
It requires that both the stock and flow of debt must be brought down. The former requires that the rate of economic growth (g) must exceed the rate of growth of debt (or the interest rate, r) for a long period, and the latter requires ensuring that the primary balance is positive.
One can think of some scenarios under which the debt reduction can materialise. The ideal scenario of growth driven by a productivity surprise (say, AI) may be too optimistic, given the need to sustain real GDP growth (g) in the 3-4% range against a real interest rate (r) at 1-2% and the ageing demographics and falling labour force participation rates. Fiscal consolidation resulting in primary surpluses is another possibility, though the very high mandatory spending plus interest (now at 75% of the budget and heading to 80% by 2036) means that austerity alone can only be a marginal contributor.
There is no historical precedent of grow out of debt at this debt level without either financial repression or fiscal consolidation alongside. The 1990s US surpluses under Clinton were a one-off combining Bush’s 1990 and Clinton’s 1993 revenue measures, the peace dividend, and the dot-com boom’s capital gains windfall.
Then there are the scenarios of Fed-led financial repression, with moderate or high inflation. However, the inflationary path requires that the debt is long duration, new issuance reprices only slightly, and the social and political consequences are managed. But the US Treasury’s weighted average maturity is only about six years, which sharply limits this pathway to debt reduction, and there may be no political tolerance for sustained inflation beyond, say, 3.5%. In any case, repression and inflation will be important factors eventually in the years and decades ahead.
They were important contributors to bringing down the debt-to-GDP ratio after the War, and the recent increase in bond buybacks announced by the US Treasury Secretary Scott Bessant are the early steps in a long period of financial repression.
This brings us to debt restructuring and haircuts, which are unthinkable for the US given that the US dollar is the reserve currency. There is also the possibility of a consolidation forced by a crisis (à la Greece), though it looks unlikely for now and may lie 10-15 years ahead.
Finally, the option of muddling through, stabilisation without meaningful reduction, is a very strong likelihood for the foreseeable future. Through a combination of mildly negative r-g through soft repression, containing primary deficits, and occasional tailwinds and reforms, debt-to-GDP can stabilise at 110-130%. Japan has run this combination for over two decades with 220-260% of GDP without any crisis, and Italy has done so at 130-140%.
For debt reduction, the US and others may find Greece an unlikely example. From a peak of 212.6% in 2021, by the end of 2025, Greece reduced its debt-to-GDP ratio to 146.1%, and it is estimated to decline to 125% by the end of the decade.
This spectacular record-breaking drop of nearly 67 percentage points within a four-year window has been achieved through a combination of strong GDP growth post-pandemic (4-5% real growth), early repayment of its financial rescue packages, negative real rates from the inflation shock, maintaining a primary budget surplus of above 2%, and concessional EU financing.
This combination of factors is unlikely for advanced countries like the US. In the circumstances, the best hope is a trend of moderate inflation (say, 3%), repression to keep interest rates down, some reversal of the accumulated tax cuts, and some expenditure reduction, all of which will only stabilise the debt at about 120-130%. This would create the conditions for deeper reforms on both the revenues and expenditure sides after a forced crisis sometime in the later part of the next decade.
A scenario which cannot be dismissed is one where the erratic policies of the Trump administration, combined with rising inflation, a supply shock (of the kind in Iran), and an AI-equity market meltdown, spook the bond markets, resulting in a significant spike in bond yields. This could, in turn, force the US Treasury into biting the bullet on revenue and expenditure-side reforms.
In the meantime, the bare minimum to calm the markets would be to at least ensure that the debt-to-GDP ratio is stabilised by bringing the fiscal deficit under control. But wars and Trump 2.0 policies work in the opposite direction.


























