Dollar General (DG), Dollar Tree (DLTR), and Five Below (FIVE) all report earnings this week. LikeFolio's Landon Swan shows his company's data highlighting the winners and losers in the discount store space. However, as Landon explains, the "trade down" mentality for American shoppers isn't going away anytime soon. He also turns to Walmart (WMT) and offers his long-term bull case for the big box retailer.