But after looking at 300 years of U.S. and U.K. history, the Center for Economic Policy Research found that wars and pandemic-scale emergencies have pummeled holders of debt.

“The historical evidence reveals a striking pattern: government bonds have repeatedly generated substantial real losses during these extreme episodes,” authors Zhengyang Jiang, Hanno Lustig, Stijn Van Nieuwerburgh, and Mindy Xiaolan wrote. “They have even underperformed equities and real estates which are traditionally regarded as risky assets.”

That’s because wars typically triggered large increases in government spending, averaging about 7% of GDP annually during the first four years, and tax hikes alone were rarely sufficient for financing needs, they added.

The finding comes as the U.S. is waging war on Iran while the national debt has exploded to $39 trillion. The Pentagon is seeking more than $200 billion in a budget request for the conflict, sources told the Washington Post.

Across their dataset, the CEPR authors calculated that bondholders suffered average real losses of roughly 14% during the first four years of conflicts. The losses were so steep that they reduced the real value of government debt outstanding.

To add insult to injury, cumulative bond returns were more than 20% below the cumulative returns on stocks and real estate, the opposite of how those assets perform during financial crises or recessions.

“Whenever there is a major war, we observe a sharp decline in the bond performance — wars are always disaster times for bondholders,” they warned. “Similarly, the bondholders also suffered large losses during the ‘war on Covid-19.’”

A key factor in bond losses is inflation, according to CEPR, which said the cumulative rate averaged about 20% in the first four years of wars.

In fact, during the current U.S.-Israel war on Iran, Treasuries and government debt from other countries have sold off sharply as surging oil prices have raised expectations for elevated inflation while budget deficits are also seen worsening. Since the war began three weeks ago, the U.S. 10-year yield has soared more than 40 basis points.

But profligate spending wasn’t the only way inflation weighed on bonds. The think tank said it was often the result of policy choices to reduce debt burdens without explicitly defaulting, such as by suspending gold standard commitments.

Another reason bonds perform so poorly during wars is so-called financial repression, or government policies that curb borrowing costs by influencing financial markets. That prevents bond yields from keeping pace with inflation.

For example, the Federal Reserve implemented yield-curve control, capped Treasury rates, and launched massive bond buying during World War II.

CEPR’s findings have particular relevance for U.S. debt as Treasuries continue to form the foundation of the global financial system with the dollar serving as the world’s reserve currency.

That status has allowed the U.S. to borrow more cheaply than investors would otherwise allow. Meanwhile, the interest on U.S. debt is now the fastest-growing budget item and is already at $1 trillion a year. CEPR said its report presents governments with an important tradeoff.

“Protecting taxpayers from large spending shocks may require shifting part of the burden onto bondholders through inflation or financial repression,” it said. “Economic theory suggests that such policies may be optimal when taxation is highly distortionary. However, they also reduce the safety of government debt and may raise borrowing costs over time if investors anticipate these risks.”