Shares of Costco Wholesale Corp. rallied 3.7% in afternoon trading Thursday, enough the pace the S&P 500's gainers, after Deutsche Bank upgraded the membership-based warehouse retailer, as recent upbeat monthly sales data supported a bullish stance. The stock, which was on track to close at a two-month high, has soared 22.5% since closing at a 10-month low of $416.43 on May 20, while the S&P 500 has lost 2.9% over the same time.