Excluding the effect of deflation in gasoline prices and the impact of foreign currency fluctuations, Costco's comps for March rose 4%, reflecting comparable sales growth of 4% both at its U.S. and international outlets. Shares of Costco Wholesale CorporationCOST fell 1.6% following comparable-store sales (comps) results for March, the five weeks ended Apr 5, 2015, that fell short of analysts' expectations. Coming to Costco, comps for the 31-week period increased 2%, buoyed by a rise of 4% across the U.S. locations, but partially offset by a 2% decline at the international locations.