Costco reports strong comparable-store sales for December, topping Wall Street expectations

Costco's sales at stores open at least a year rose 3 percent in December, beating Wall Street's estimate.

Analysts polled by Thomson Reuters expected a 2.8 percent increase in the figure.

Sales at stores open at least a year is a key gauge of a retailer's health because it excludes the volatility from recently opened or closed stores.

In the U.S., those sales climbed 5 percent. They fell 1 percent overseas.

Stripping out the impact of lower gas prices and foreign currency exchange fluctuation, sales at stores open at least a year gained 8 percent at home and abroad.

Total revenue for the month climbed 5 percent to $12.12 billion.

For the 18 weeks ended Jan. 4, sales at stores open at least a year rose 4 percent. They climbed 6 percent in the U.S., but were flat overseas.

Excluding the impact of lower gas prices and foreign currency exchange fluctuation, sales at stores open at least a year the figure rose 7 percent. It also increased 7 percent in the U.S. and internationally.

Total revenue for the 18-week period climbed 7 percent to $40.85 billion.

Costco Wholesale Corp., based in Issaquah, Washington, runs 671 warehouses, including 474 in the U.S. and Puerto Rico, 88 in Canada, 34 in Mexico, 26 in the U.K., 20 in Japan, 11 in Korea, 10 in Taiwan, seven in Australia and one in Spain.