Why has Costco's stock fallen 14% since its record high in May? On the surface, it doesn't seem to make sense. Shoppers love the wholesale retailer for its bulk groceries and $1.50 hot dogs, both in times of economic dips and prosperity. In actuality, Costco could be the victim of its own success — executive editor Joe Ciolli explains why. #costco #wholesaleshopping #stockmarket #stocks #firsttrade