Key TakeawaysHigher-income households are increasingly Walmart shoppers. The retail giant said market-share gains were "primarily" driven by wealthier households in the latest quarter.Executives said that while shoppers across income levels are attracted by lower prices, wealthier ones are also choosing Walmart for service and convenience. Higher-income households are increasingly Walmart (WMT) shoppers.  The retail giant, shares of which were surging more than 6% in intraday trading Thursday after the comp ...