Gross margin performance of publicly reporting supermarket companies Albertsons Cos. (ACI), Kroger Co. (KR), Walmart (WMT), Village Super Market (VLGEA), Sprouts Farmers Markets (SFM), Natural Grocers by Vitamin Cottage (NGVC), Publix Super Markets (PUSH), Grocery Outlet (GO) and Ahold Delhaize (AHODF)