Public Debt and the Arithmetic of Time

Public debt, in the form we recognise today, takes shape in late seventeenth‑century England. States had borrowed before—Italian city‑states had done so for centuries—but this is the moment when sovereign credit becomes not merely a fiscal instrument, but a stable, credible and widely tradable one. Confronted with the costs of war against Louis XIV, William III looks beyond taxation and turns, with some hesitation, to the capital markets.

The difficulty is one of memory. Barely two decades earlier, the English crown had defaulted on London goldsmiths—who, in a world without central banks or formal regulation, served as bankers in all but name.

The solution arrives from an unexpected quarter. William Paterson, a Scottish merchant, proposes a deceptively simple idea: rather than relying on a handful of wealthy lenders, borrow from a broad base of smaller ones. The savings of merchants, landowners and the emerging middle classes become the foundation of public finance. From this arrangement emerges the Bank of England, a joint‑stock company partly owned by the state and entrusted with managing and guaranteeing the loan.

The earliest government securities are hybrids: fixed interest combined with a form of participation in the new institution. Sovereign credit ceases to depend on a narrow circle of financiers and instead draws upon the accumulated surpluses of many. The crown gains twice—lower interest rates and reliable access to funding. Over time, Treasury bills evolve from this system and become a defining feature of modern economies.

Today, sovereign credit is so ubiquitous that questioning its role can seem almost frivolous. Mainstream economics tends to cast the state as a prudent planner, smoothing cycles and financing productive investment through debt. It is an elegant, optimistic view.

Reality is rather less forgiving. Each increase in public debt entails a larger future burden, driven by compounding interest. Borrowing is defensible only when the returns on public projects exceed the cost of financing and when loans are ultimately repaid. Yet global trends suggest otherwise. Public debt relative to GDP continues to rise across most advanced economies, gathering momentum like a snowball rolling downhill.

In principle, rising debt might indicate sustained investment in profitable ventures, undertaken because tax revenues are insufficient. In practice, structural deficits have persisted for decades. More plausibly, debt expands because returns fall short of financing costs, and maturing obligations are rolled over rather than retired. Interest accumulates. Debt rises—not to foster growth, but to avert default.

Governments face two choices: raise taxes or refinance. Higher taxes depress living standards for those who do not hold government securities, but they address the underlying imbalance. Refinancing merely postpones the reckoning. The total owed grows until markets judge it unsustainable, at which point default becomes more than a theoretical possibility.

This dynamic enables the present generation to consume beyond the economy’s real capacity, shifting the burden—plus interest—onto the future. Some of those who will bear the cost are not yet born, which conveniently reduces political pressure to act. The notion that fiscal burdens will ease over time collapses when debt grows faster than revenue. In the United States, public debt has multiplied over the past half‑century, while median incomes have lagged markedly behind.

To be sure, some public spending finances goods whose returns are diffuse or difficult to quantify—healthcare, security, defence. Their benefits may spill over into productivity and growth. Yet when such expenditures rely on persistent deficits, the implication is clear: society is consuming more than it can sustainably afford, leaving the bill to posterity.

Finance students are taught that sovereign bonds are “risk‑free.” In developed economies, outright default is indeed rare. Treasury operations are generally managed with care. True—but incomplete. Inflation constitutes a subtler form of debt restructuring. Policies such as quantitative easing can erode the purchasing power of bondholders. When unexpected, inflation affects not only institutions and pension funds but also ordinary savers. It becomes, in effect, a future debt write‑off funded by past thrift.

The consequence is a gradual erosion of trust. To attract new lenders, governments must offer higher rates—compensating for inflation and perceived risk. Once expectations are disappointed, the likelihood of a conventional default increases.

Two perspectives help explain the persistence of public debt. First, Keynes’s reminder that “in the long run, we are all dead.” Those who benefit today are not necessarily those who will pay tomorrow. Deferral creates moral hazard. Ricardian equivalence holds only if debt is repaid within a generation or if individuals care as much for future generations as for themselves—assumptions that rarely hold.

Second, Mancur Olson’s “stationary bandit.” The state monopolises coercion, but governments are temporary. Facing uncertain re‑election, they prioritise short‑term advantage. Spending rises. Debt accumulates. The costs fall on future administrations, perhaps of different political persuasions. Public debt becomes structural rather than exceptional—a predictable outcome of political incentives.