Retailers are reporting weak sales for June as worries about the economy and jobs are making shoppers pull back on spending. The results raise concerns about Americans' ability to spend for the back-to-school shopping season. As merchants reported their sales early Thursday, many of them disappointed. Costco Wholesale Corp. reported a gain below Wall Street expectations. Target Corp. also missed estimates, posting a modest increase. Teen retailer Wet Seal Inc. reported a bigger-than-anticipated decline. One bright spot was Limited Brands, which reported a robust gain that surpassed Wall Street predictions. The figures are based on revenue at stores opened at least a year. They are considered a key indicator of a retailer's health because they exclude the impact of newly opened and closed stores.