Credit card issuers have to be smiling about their good fortune in April.

Revolving credit rose by $5 billion in the month, after edging up $1.4 billion in March, the Federal Reserve Board reported Tuesday.

Overall, consumers borrowed $8.9 billion in installment loans in April, the Federal Reserve said - the largest one-month hike in nearly a decade.

The seasonally adjusted monthly change in credit outstanding stood at a revised $8.4 billion in March, up from the $7.4 billion the Fed originally estimated.

Revolving credit accounted for about half of the overall increase, the report said.

Installment loans include credit card debt, automobile loans, and other personal loans. Economists have been encouraged by the consumer installment numbers that have risen for 11 consecutive months, but the sharp rise in credit card use had some puzzled.

Consumers are spending beyond their incomes, said James Annable, chief economist for First Chicago Corp., which suggests that savings have gone down. "You have to scratch your head and ask how are people doing that?"

A few months earlier, he said, consumers used money from refinanced mortgages to make new purchases. Now they are looking for new credit lines, including home equity loans and credit cards. "That means this is in reality a short-lived phenomenon."

The installment credit boon can also be associated with the huge increase in homebuying at the beginning of this year. To fill those homes, Mr. Annable said, consumers are buying appliances and furniture and putting those purchases on credit cards.

Meanwhile, credit card issuers have provided multiple incentives to get consumers to put purchases on their cards, noted James Chessen, chief economist for the American Bankers Association, citing a rash of value-added card offers.

"All of this suggests that consumption will no longer be the engine of the economy," Mr. Annable said. "The economy will have to slow."

Consumer installment credit rose at the annual rate of 13.2%, while revolving credit rose at a 20.7% rate. Automobile credit expanded at a 11.9% annual rate and personal loans at 5.5%, the Fed reported.

Growth of auto and other loans slowed in April, the Fed reported. Consumers borrowed $2.8 billion in auto loans in April, down from $3.8 billion in March. Other loans dipped from $3.3 billion to $1.1 billion.

Mr. Chessen said he will be watching closely to see if the expansion of consumer debt will be followed by higher loan delinquencies.

"If consumers are using credit installment loans, particularly credit cards, because their financial situation is tight, that gives me cause for worry," he said.

The big jump in April may be because of income tax payments, which were such a burden that consumers had to put purchases on credit cards, Mr. Chessen observed. "That says they were not in such control of their finances."

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