France's bond market turmoil and the mass student protests sweeping the country's schools are not a coincidence, but rather the product of generational tradeoffs in government spending, according to Nobel laureate economist Paul Krugman.

In a Substack post published Thursday, the economics professor at the City University of New York's Graduate Center acknowledged that the high debt and deficits recently driving up French bond yields are not unique to the eurozone's second-largest economy. The United States, he noted, is guilty of the same fiscal sins, particularly as aging demographics push entitlement spending higher faster than revenue comes in.

"But France does stand out, even among fiscally troubled nations, in one main way: its persistent inability to get realistic about retirement," Krugman wrote.

France's official retirement age, at which workers can collect full benefits, stood at just 62 in 2023, while the average actual retirement age of 60.4 years was the lowest in Western Europe. Those eligibility ages carry outsize weight in budget math, since each year of earlier retirement means more time collecting benefits and fewer years paying in.

Meanwhile, French students have taken to the streets to protest missing teachers, run-down classrooms, and buildings that are not equipped for rising temperatures, blaming years of underinvestment in public education.

Krugman drew a straight line from France's retirement largesse to the student unrest, highlighting the generational tensions over how public resources are allocated between baby boomers and the country's youth.

"Thus the fiscal pressure caused largely by France's very generous government pension plan has led to cutbacks in other spending, notably on education," he wrote. "France is effectively handing over large subsidies to older French at the expense of everyone else. Mass national student demonstrations should come as no surprise."

U.S. debt is likewise on an unsustainable trajectory as spending on seniors climbs amid more baby boomer retirements, although even some Republicans have expressed openness to tax hikes to keep Social Security's trust fund solvent.

French President Emmanuel Macron, for his part, attempted to raise the retirement age to 64, but intense political pushback has stalled those efforts. Marine Le Pen, the far-right front-runner in France's presidential election next year, has vowed to roll the official retirement age back to 62 and has previously suggested dropping it to as low as 60. With the presidential vote approaching, the collision between pension promises and fiscal arithmetic looks set to remain at the center of both French politics and investor scrutiny.

" would be extremely expensive and is symptomatic of a general unwillingness on the part of France's rising right to face reality," Krugman said. "Again, this is hardly unique to France — think of all the false promises and claims Donald Trump has made. But for now, at least, financial markets believe that fantasy economics is an even bigger problem for France than for the rest of us."

Markets are indeed pricing in growing odds of a French debt default, a risk investors monitor through the credit default swap market, where contracts work much like insurance against a borrower failing to repay. Earlier this month, French 10-year bond yields jumped to their highest level since 2002, and the premium over equivalent German yields — a closely watched barometer of perceived sovereign risk in the eurozone — widened to its largest since the eurozone debt crisis of 2011.

Those metrics later eased, but France's fundamentals remain troubling, with anemic GDP growth, a budget deficit estimated at about 5.4% of GDP — well above the European Union's long-standing 3%-of-GDP reference value — and rising debt-service costs as yields jump, since maturing debt must be rolled over at prevailing rates. The country's debt-to-GDP ratio, a measure of what a government owes relative to the size of its economy, is expected to climb to 122% next year from 119% this year, and the government's latest plan failed to halt the surge in bond yields as investors doubted its credibility.

Thierry Wizman and Gareth Berry, global strategists at Macquarie, have also drawn a connection between the French debt crisis and the student protests. In a note Wednesday, they warned that the longer the protests go on, the more likely it is that the government will cave and approve more spending, which would make the debt situation worse. That would drive up yields on French bonds, making borrowing to fund that spending even more expensive — and in turn deepening the very problem the demonstrators are complaining about.

"France is veering toward a full-blown civil crisis because of its political polarization, which heretofore had been manifested mainly in the political realm itself, and at the ballot box only," they wrote. "And rather than being isolated events, we think a direct and self-reinforcing causal connection can be drawn between the rise in France's debt yields and the street riots of the past few days."

This story was originally featured on Fortune.com.