NEW YORK » Credit card interest rates are climbing. It’s just not clear exactly why.

A study released Tuesday suggests that today’s higher rates are mainly a reflection of the struggling economy. That’s contrary to the credit card industry’s refrain that tighter regulations have forced banks to pass costs along to consumers.

The average credit card rate rose to 13.44 percent at the end of last year, from 12.75 percent on the eve of the Great Recession, according to data from the Federal Reserve. Most cards have variable interest rates, however, meaning their rates rise and fall with the prime rate.

The study by CardHub.com examined the movement of the average interest rate after subtracting the prime rate. This helps gauge how card issuers adjust the portion of the interest rate they control.

That margin interest rate jumped from 5.25 percent just before the recession to a nearly two-decade high of 11.01 percent in February of last year. But much of that jump took place before the new credit card regulations were signed into law and well before they took effect a year later. Card issuers were likely responding to rising delinquency rates in an increasingly uncertain economy, according to CardHub.com.

The study also notes that the margin interest rate was even higher during the 1990s, when the country was going through a less severe recession with lower unemployment and credit card delinquency rates. In August 1992, the margin rate was 11.68 percent.

It might also surprise some that the margin rate has actually eased slightly since the new regulations took effect in February of last year. The rate was 10.59 percent at the end of last year.

Under the new regulations, card issuers can no longer hike interest rates on existing balances or in the first year after an account is opened. After that, issuers can increase rates on new charges, but must give 45-days notice before doing so. Late fees and other penalty charges are also capped at $25 per violation.

The broader economic climate — along with the new regulations — no doubt factors into the higher interest rates and tightened credit market, said Peter Garuccio, a spokesman for the American Bankers Association. But he noted that it was impossible to determine how much of a role either one played.

"The CARD Act has been a net positive for consumers, but there have been some tradeoffs," Garuccio said.

For example, he said that it wouldn’t be a surprise if interest rates continue climbing even as the economy improves, given the estimated billions of dollars in revenue card issuers stand to lose as a result of the new regulations.

It’s doubtful that card holders across the board are seeing higher rates, however, notes Odysseas Papadimitriou, founder of CardHub.com. Instead, he said credit card issuers are likely selectively imposing the harsher terms on those with less-than-stellar credit.

That’s because this group has become less profitable in the aftermath of the new consumer protections.

Another reason interest rates are bound to continue climbing? Most cards have variable rates. And as the economy improves, the prime rates they’re tied to are likely to rise as well.