Despite a tough consumer environment, Costco Wholesale Corp. 's ( COST ) comparable-store sales results for January bettered analysts' expectations. Excluding the effect of gasoline prices and foreign currency fluctuations, Costco's comparable-store sales for the period jumped 5%. Excluding the effect of deflation in gasoline prices and adverse impact of foreign currency fluctuations, Costco's comparable-store sales for January rose 6%, reflecting comparable sales growth of 5% at its U.S. locations and 8% at international outlets.