NEW YORK (AP) — Americans would save roughly $100 billion a year in interest costs if President Donald Trump’s campaign proposal to cap credit card interest rates at 10 percent were implemented, according to a paper published by Vanderbilt University.

Further, the banks and credit card companies would be able to withstand, and even still be profitable, if there were a national cap on interest rates. While limited in scope, the paper gives some academic backing to Trump’s campaign promise.

The paper found that banks would still be able to earn a profit on most of their customers even if credit card interest rates were capped at 15 percent, and if the banks continued to offer rewards and perks such as points and airport lounge access. If interest rates were capped at 10 percent, the business model gets more difficult for the banks, but they could still make money off most card customers by cutting back on some rewards.

Usury laws are as old as the Bible but have gotten traction again through Trump’s populist politics. When he was a candidate in the 2024 election, Trump proposed a temporary 10 percent cap on credit card interest rates. He has not spoken about it since the election.

That said, politicians have seized on the idea. Sen. Josh Hawley, R-Mo., and Vermont Sen. Bernie Sanders introduced a bill in Congress that would match Trump’s campaign proposal of capping interest rates at 10 percent. A similar bill was introduced in the House by Rep. Alexandria Ocasio-Cortez, D-N.Y.

The banking industry is adamantly against any caps on credit card rates. Historically, the industry has argued that any cap on interest rates would decimate the credit card business model and would threaten the viability of popular rewards and perks programs that millions of Americans use for free flights and hotel stays.

Americans are carrying more credit card debt than ever before, to the tune of $1.21 trillion, or roughly $6,400 per person. The average credit card interest rate is approximately 21 percent, according to data from the Federal Reserve. That’s significantly higher than a decade ago, when the average credit card interest rate was about 12 percent.

Banks earn revenue from credit cards two different ways: the amount of money they charge merchants to process a credit card transaction, often referred to as interchange, and the interest and fees the banks charge customers. That could be the annual fee on a credit card, or the monthly interest that accrues when a customer carries a balance.

The Vanderbilt paper suggests the revenue earned from interchange is why banks would remain profitable, even if credit card interest rates are capped. Credit card rewards programs are largely funded through interchange. American Express, for instance, earned $35.2 billion in revenue from the fees they charge merchants.