Why the U.S. Treasury market is like a rom-com

At a Senate hearing earlier this month, economist Martha Gimbel compared a wonky thing, the U.S. Treasury market, to something very relatable, a Hallmark rom-com.

Why it matters: She hit at the essence of what's confounding experts in government debt:

• Why haven't bond investors penalized the U.S. for its erratic policymaking and weakening institutions by meaningfully driving up the country's borrowing costs?

The big picture: Gimbel and other experts believe that the answer is that there's not yet a good alternative to the enormous market for Treasurys, so investors stick with the "cleanest dirty shirt."

• "People think that U.S. Treasurys are the only large safe asset, so people are still buying them," Ugo Panizza, an economist and director of the International Center for Monetary and Banking Studies, told Axios earlier this year.

The U.S. is "currently the boyfriend at the beginning of the Hallmark movie in the big city, where the girlfriend is still going out with him, even though she knows that it's wrong," Gimbel, executive director of the Yale Budget Lab, put it.

• "But at some point, it, she's going to go home to the small town and find the nice firefighter and realize that there's another option."
• "And we don't know when that will happen."

Between the lines: Metaphors are good for getting people's attention on issues that are hard to grasp.

• Gimbel even got a laugh out of the room — no small feat at a hearing before the Senate Subcommittee on Fiscal Responsibility and Economic Growth.

What to watch: If investors ever find a better option than Treasurys, that would be a huge problem given that we are borrowing a lot of money right now.

The latest: The energy shock driven by the Iran war has helped drive up the yields on U.S. debt.

• The MOVE Index, which tracks volatility in the Treasury market, is spiking above its 52-week average — as it has during other moments of economic shock.
• "Investors' concerns include an unsustainable American fiscal position, rising inflation risk and a growing uncertainty about war," RSM chief economist Joseph Brusuelas wrote in a note Wednesday.

How it works: There are reasons for investors to be wary of buying sovereign debt.

• Governments are hard to sue, and it's difficult to enforce your claims against them.
• "They can do things that private companies can't, like pass laws and inflate their currencies," Panizza and University of Virginia international law professor Mitu Gulati explained in a piece for Reuters last summer.

Zoom out: That's why the countries that attract the most investors are the trustworthy ones with strong institutions. They are rewarded with lower borrowing costs.

• 17th-century England is the textbook example. It was able to borrow more because it had effective institutions that checked the king's temptations, per a well-known paper from 1989.
• This helped the country become a superpower.

What they're saying: The U.S. is still considered exceptional among investors, says Layna Mosley, a professor of politics and international affairs who directs the Princeton Sovereign Finance Lab.

The bottom line: Investors still see the U.S. as the safest bet around, but if ever a new hometown hottie materializes — watch out.