American Express's third-quarter profits soared 71% as customers increased their spending by 14%, and receding losses from souring card loans allowed the company to squirrel away less for a rainy day.

AmEx's results offer an insight into the rising optimism of its borrowers-mostly well-heeled consumers and companies-as the economy stabilises despite stubbornly high unemployment. The company's performance also cements the turnaround in the credit-card industry.