US consumer credit increased at an annual rate of 8.3 percent in May, a bigger gain than the prior month, the U.S. Federal Reserve reported on Monday. Total consumer borrowing rose from a revised 2.8197 trillion U. S. dollars in April to a seasonally adjusted 2.8393 trillion dollars in May. Revolving debt, the type which includes credit cards, rose to 856.5 billion dollars in May, up 9.3 percent at an annual rate from the revised figure in April. The borrowing in the non-revolving category that includes auto and student loans, rose at an annual rate of 7.9 percent to 1.9828 trillion dollars. Consumer spending, which accounts for about 70 percent of the overall U.S. economic activity, was the major engine of U.S. economic growth. A rise in consumer credit indicated consumers boosted their borrowing on spending.