Credit card interest rates rose slightly this week after Barclays raised interest rates on two of its cards.

The national average annual percentage rates for new credit card offers climbed to 14.71% this week, according to the CreditCards.com Weekly Credit Card Rate Report. It's just the second increase since early November, but it pushes the national average to its fourth highest level since CreditCards.com began tracking rates in mid-2007.

This week's APR changes were spurred by significant rate hikes that Barclays made on two of its rewards cards. Barclays raised the bottom end of the APR range on its U.S. Airways Premier World MasterCard only slightly, from 15.24% to 15.99%. However, the range's top end shot up more than 6% points to 24.99% -- making it a far pricier card for consumers with poor credit. For example, if a cardholder who qualified for the card's highest annual rate borrowed $5,000 on the card and paid $150 monthly, that cardholder would have to pay $1,767 more in interest than they would have paid before the change. (Calculator: How long will it take to pay off your credit card balance?)

Barclays also bumped the APR on its upscale Visa Black Card from a flat 13.24% to 14.99%, making the Black Card slightly more expensive than the national average. In addition, its annual fee -- $495 -- is among the highest in the industry.

Barclays confirmed the changes, but they didn't offer any further comment about the moves. However, experts say the Black Card's recent rate hike may also be part of an overall shift in strategy by issuers of high-end, high-fee cards.

Mail offers for high-end cards dropped in 2010
At the peak of the recession, issuers mailed fewer credit card solicitations overall, according to Synovate, a global market research firm that tracks credit card mailings. However, issuers mailed significantly more offers for high-fee cards, such as the Black Card, to consumers who they believed would be more likely to pay off their debt -- so-called superprime card holders. "The reason this dichotomy arose was due to the fact that issuers were waiting to get clarity on the Credit CARD Act," said Synovate's Anuj Shahani in an e-mail, referring to the landmark, pro-consumer credit card industry regulations that took effect in 2010. "The financial crises had not been abated as much, making issuers move to the superprime segment (more than usual) and market more high-end cards as they seemed to be the 'safe-haven.'"

That trend may be reversing. As the economy improves, Synovate is seeing more credit card solicitations being sent, with fewer going to high-end consumers. For example, the number of mailings featuring cards with an annual fee of $250 or greater has dropped precipitously in the past year.

Rewards cards are becoming more expensive for some
Although most banks remained quiet over the New Year weekend, Barclays wasn't the only bank in recent months to raise interest rates on its rewards cards. According to CreditCards.com data, many of the country's most popular rewards cards have recently become significantly more expensive for average consumers who don't qualify for the cards' lowest rates. In the past six months, 20 of the 58 rewards cards that CreditCards.com tracks have increased the top end of their APRs, many by several percentage points. This kind of spike in rates, particularly for rewards cards, can be dangerous for consumers who can't afford to pay off their balance at the end of each month.

And many rewards card holders find themselves in just that situation. According to a study released last month by the Federal Reserve Bank of Chicago, rewards cards that offer cash back incentives, such as 1% cash back, often lead consumers to spend more each month and accrue a higher month-to-month balance. The study found that consumers tend to use their rewards cards in place of other credit cards and increase their overall debt in the process. "Our results confirm that cardholders not only increase spending but also their debt," the authors concluded in the study.

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