Record issuances, refinancing and absorption capacity: the risk is not default, but liquidity
When the subject of public debt arises, the mind almost instinctively turns to a very simple idea: sooner or later, someone will not pay. Default — the sudden rupture, the event that marks a before and after. It is an intuitive image, reassuring in its clarity. But it is also, in the vast majority of cases, misleading.
In today’s financial markets — particularly in advanced economies — the real stress test is not the formal insolvency of a sovereign state. It is something more subtle and, precisely for that reason, more insidious: liquidity. The capacity of the system to absorb ever-greater quantities of debt, to refinance it without friction, to reconcile it with higher interest rates and with a volatility that is no longer suppressed as it was in previous years.
The risk is not so much that a state “fails to pay”. The risk is that the market, at a certain point, struggles to allow it to pay on the same terms as before.
From debt “in theory” to debt “in practice”
To understand why liquidity is today the real critical point, one must shift perspective. It is not enough to look at how much debt exists. One must look at how much debt is moving.
Public debate often focuses on the stock: the debt-to-GDP ratio, absolute levels, cross-country comparisons. These are important figures, but they tell only part of the story. The decisive element lies in the flows: how much new paper is being issued, how much is maturing, how much must be refinanced, at what frequency and at what price.
Every instrument that matures is not a neutral event. It is a market event. The state must repay the principal and, in most cases, does so by issuing new debt. It is a continuous relay race: as long as the relay runs smoothly, nobody notices. When, however, the number of runners increases, the pace accelerates and the terrain becomes treacherous, the risk is not that someone falls immediately, but that the race becomes disorderly.
And this is where stress originates.
Why the market absorbs gross debt, not “net” debt
There is a point that often goes unnoticed, yet is central to understanding the fragility of moments of tension. The market does not absorb net debt. It absorbs gross debt.
If a state issues 300 billion in new securities and redeems 280 billion over the same period, the net borrowing requirement is only 20 billion. But for the market, this detail matters little: it must still find buyers for 300 billion of new paper. Those instruments compete for the same liquidity as everything else in the financial system.
There is no “preferential lane” for public debt. There is a market that must decide where to allocate capital, at what price and under what constraints. When volumes become very large and frequent, the question is no longer whether the debt is sustainable “in theory”, but whether it is operationally sustainable, day after day.
The regime shift: when the central bank is no longer the dominant buyer
During the years of zero interest rates and massive central bank purchases, the absorption problem seemed almost non-existent. A very large share of demand was not price-driven, but driven by monetary policy. Volatility was suppressed, interest rate risk was marginalised, and duration was almost given away for free.
Today the context is different. Not because central banks have suddenly become “hostile”, but because the price of money has come to matter again. The yield is no longer a minor detail, duration is no longer neutral, volatility is no longer background noise.
This means that demand for public debt is more selective. Investors require a clearer premium for committing capital over the long term, are more sensitive to price movements, and more attentive to the true liquidity of the instruments they purchase. In this environment, absorption is not guaranteed: it must be earned.
Where stress originates: auctions, intermediation and leverage
Stress does not arise suddenly. It accumulates in operational mechanisms.
Auctions, for instance, are a first thermometer. When demand is robust, securities are placed without difficulty. When the market begins to demand a higher premium, this becomes immediately apparent: rising yields, thinner cover ratios, greater dispersion between supply and demand.
Then there is intermediation. Dealers play a crucial role as a bridge between the sovereign and end investors, but they are not limitless warehouses. They operate under constraints of capital, leverage and funding costs. When these constraints tighten, their capacity to temporarily absorb large volumes diminishes.
Finally, there is leverage. Much of modern finance uses very short-term financing to support larger positions. As long as liquidity is abundant, the system holds. When the cost of funding rises or volatility increases, leverage contracts. And the contraction of leverage often arrives at the worst possible moments, amplifying price movements.
No default is required to trigger this process. A friction in liquidity is sufficient.
Why the real risk makes no noise
Default is a clear, almost theatrical event. It has a date, an announcement, a headline in the newspapers. A liquidity crisis, by contrast, is silent. It begins with small signals: widening bid-ask spreads, sharper price movements, changing correlations, instruments that suddenly become “less liquid” precisely when they are needed most.
This is why it is more dangerous. Because it does not present itself as a rupture, but as a series of adjustments which, taken together, alter investor behaviour and overall financial conditions.
A sovereign state may be perfectly solvent and, at the same time, generate instability if the market struggles to absorb its debt on previous terms. In that case, it is not the repayment that breaks down. It is the equilibrium.
What this means for investors
This subject is not confined to specialists. It has very concrete implications for portfolios.
If the primary risk is liquidity, then duration management becomes a deliberate choice, not an automatic one. Diversification cannot be limited to multiplying instruments, but must take into account different market regimes. True liquidity — the kind that remains liquid even in moments of stress — becomes a strategic resource once more, rather than a drag.
Above all, it becomes essential to understand how instruments behave when the context changes: those that appear efficient during calm phases may prove fragile when liquidity withdraws.
In conclusion
Global public debt is not a problem because it is “too high” in an abstract sense. It is a challenge because it must be continuously refinanced in an environment where the price of money has come to matter again and liquidity is no longer guaranteed.
The real stress test for markets is not the capacity of sovereign states to pay, but the capacity of the system to absorb enormous flows of debt without losing equilibrium. And it is precisely in moments when everything appears to be functioning that it is worth looking more carefully at what makes no noise: liquidity.