By 2009 the top four food retailers controlled more than half of all grocery sales
"By 2009, the top four food retailers — Wal-Mart, Kroger, Costco and Supervalu— controlled more than half of all grocery sales."
Food and Water Watch, "Consolidation and Buyer Power in the Grocery Industry," Fact Sheet, December 2010 http://documents.foodandwaterwatch.org/doc/RetailConcentration-web.pdf
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