A single nation-wide grocery chain should be enough to establish trends - that's how statistics work. The report is looking at broad categories of foods (soft

A single nation-wide grocery chain should be enough to establish trends - that's how statistics work. The report is looking at broad categories of foods (soft drinks, vegetables). Walk into any Kroger, Whole Foods, Von's, or Trader Joe's and you'll the same assortment of products at similar levels of inventory. Demand shifts take many years and even decades, and grocers use that data very effectively for inventory control management. Even without controlling for multiple chains, I'd wager the numbers are in the ballpark of the expected value.