Consumers Use Credit Cards for Necessities as Inflation Cuts U.S. Incomes

``The swings in purchases of fuel and food have been "dramatic," Tavares said. The volume of gasoline purchases placed on credit cards jumped 39 percent last month from a year earlier, compared with a 21 percent increase in June 2010, he said. Food shopping increased 5 percent after falling 7 percent last year. The value of an average transaction on credit cards outpaced the gain for debit cards, showing consumers are increasingly relying on borrowing to pay for gasoline and other necessities, Tavares said. ''