Despite falling interest rates, a growing number of consumers are paying the same — or even more — to borrow on their credit cards.

The majority of credit cards on the market have variable, or floating, rates. Theoretically, that means that as the Federal Reserve lowers its federal funds rate — the latest cut took place this month — cardholders should also see their borrowing costs fall.

In reality, though, banks often set a "floor" that credit card rates can't fall below, and in many cases, that floor has already been reached, analysts say.

Wells Fargo, HSBC, Discover, SunTrust, PNC and National City have a floor on at least some of their credit cards. Wachovia, meanwhile, limits how far its penalty interest rate — applied to consumers who pay late twice in a row — and cash advance rate can drop. But the bank imposes no minimum interest rate on credit card purchases.

Others, including Bank of America, American Express and U.S. Bank, say they have no floors on credit card rates. Chase and Citigroup, meanwhile, declined to disclose whether they have this policy.

Imposing a floor on credit card rates allows the bank to "continue lending even in challenging environments," says Todd Morgano, a spokesman for National City.

But such interest rate restrictions mean that borrowers with good credit may not see their rates fall below 10 percent while those with bad credit may not see rates lower than 20 percent, says Greg McBride, a senior analyst at www.Bankrate.com.