ISSAQUAH, Wash. — Costco Wholesale Corp. posted a 17% increase in profit for the first quarter ended November 21, helped in part by a 10% increase in membership fee income, and a 7% increase in same-club sales worldwide.

Costco Wholesale Corp. posted a 17% increase in profit for the first quarter ended November 21, helped in part by a 10% increase in membership fee income, and a 7% increase in same-club sales worldwide.

The company also appears to be benefiting from economic recovery in Southern California.

"Costco’s Southern California regions were once the company’s most profitable by far," says ThinkEquity LLC analyst Edward Weller. "Those regions account for almost of third of U.S. sales, almost a fourth of total sales, and recovery there — continued recovery — could have a very favorable impact."

Weller pointed out that Costco’s membership trends are extremely strong, with renewal rates at all-time highs and more members upgrading to Executive status. Costco members are also visiting the clubs more often, and spending more when they do.

The improved results, with same-store sales advancing 5% in the United States and 14% in international markets, suggest that, for Costco’s upscale members at least, economic conditions are improving. Costco’s outlook, meanwhile, remains upbeat.

"We entered the holiday season strong and still feel that way," chief financial officer Richard Galanti told analysts during a conference call.