Brisbane, CA-based comparison shopping Website Shopping.com debuted on the Nasdaq stock exchange Monday with an initial public offering of $18 per share. Traded under the ticker symbol “SHOP,” the shares of the e-commerce site closed Monday at $28.80, up more than 62% from its morning debut. By Wednesday shares of the stock were trading for $33.08. Shopping.com gathers product and merchant data and organizes it into a catalog that compares prices Internet retailers charge for products.