"They have maxed out their credit limits," Castro-Wright said in an interview after a speech in Los Angeles. "That decline in credit means people have to make choices about how they spend their hard-earned money," he said, USA Today reported Wednesday.

Wal-Mart stores found credit card use dropped sharply in the second quarter of 2008, the newspaper reported. As a result, shopping for necessities has surged at the beginning of the month, when consumers have cash to spend.

Wal-Mart customers are also shying away from purchasing unnecessary items and name-brand products.

"Customers are really going through some hard times," Castro-Wright said.