I don't know how it is in Europe, but here in Canada, looking at grocery stores in isolation makes little sense when most of the market is controlled by a handful of vertically integrated conglomerates. On top of the stores, they own a lot of the distribution, wholesale operations, real estate, and even some suppliers. Their own financials show record revenue and profit, year after year, and their margins have increased significantly over the last few years too. We can't reduce the economics of such integrated corporate groups to their retail net margins alone to judge profitability. As far as Canada goes, small margins my ass.