Costco Wholesale ( COST ) said same-store sales in April fell 8%, while total sales for the four weeks ended May 3 fell 6% to $5.18 billion from $5.54 billion a year earlier. U.S. same-store sales at the warehouse retailer fell 7%, while international sales declined 12%. The latest four weeks included 27 days of sales compared with 28 last year, reflecting the timing of Easter. In a press release Thursday, Costco estimated the calendar shift to have hurt same-store sales and total sales by about 2% to 3%.