Warehouse club operator BJ's Wholesale Club Inc. said its same-store sales grew 1.6% in December as lower gasoline sales weighed on results. Analysts, on average, expected a 3.1% increase in same-store sales, according to a poll by Thomson Reuters. Same-store sales, or sales at stores open at least a year, are a key measure of retailer performance because they measure growth at existing stores rather than from newly opened ones. Excluding gas sales, same-store sales grew 5.9%, surpassing Wall Street's expectations for 1.6% growth. For January, BJ's expects to report a 6% increase in same-store sales, excluding gasoline sales.