WASHINGTON — Americans boosted their borrowing by 7.73% in October from a year ago, the largest increase in nearly a year as consumer spending has helped fuel U.S. economic growth. The Federal Reserve says consumer borrowing rose by a seasonally adjusted $25.3 billion in October to a total of $3.96 trillion. The October increase was more than double the gain in September. Much of the increase was due a 10.75% jump in revolving credit, a category that includes credit cards. Non-revolving credit — which includes auto loans and student debt — rose 6.67%. Economists and investors monitor consumer borrowing to judge the willingness of people to take on debt to finance their purchases. Higher debt can suggest that people are confident in their ability to repay their loans.