Amex hikes rates for 1 million customers

Given a change to American Express (AXP) cards, some customers might be tempted to leave home without it.

The lender is raising interest rates on more than a million cards, marking the first such move in more than five years, according to Bloomberg News. American Express didn't immediately return a request for comment.

Annual rates will climb an average of 2.5 percentage points to at least 12.99 percent. According to letters sent to customers, Amex explained it was making the adjustment after finding that consumers with similar credit profiles were charged higher rates by rivals, Bloomberg reported. While that might be the case, it's unusual for lenders to boost rates without an underlying change in the interest-rate environment or with a change in risk.

While the Federal Reserve is widely expected to begin hiking rates later this year, the central bank's benchmark rate has been held near zero for nearly six years. As the economy has strengthened, the delinquency rate on credit-card debt has declined, dropping to 1.47 percent in the third quarter from 1.5 percent in early 2013, according to TransUnion, a credit-reporting company.

The rate increases will impact variable-rate products including some of its proprietary and co-branded cards, Amex told Bloomberg. The higher rates will only affect a small share of the company's customer base, given that it has more than 42 million U.S. cards in circulation.

The move comes amid several recent dings to Amex's business. Earlier this month, American Express said that its exclusive partnership with wholesale retailer Costco (COST) would come to an end on March 31, 2016. The parting is a major loss for Amex, given that Costco-related cards are responsible for one-fifth of its loans.

On top of that blow, Amex lost an antitrust lawsuit this month, with a U.S. District Court deciding that its merchant rules were anticompetitive. American Express has said it will appeal the ruling.

Shares of American Express are down nearly 12 percent this year, while the S&P 500 index has risen 2.8 percent during the same period.