In an editorial criticizing Vice President Kamala Harris for her speech on Friday, the Washington Post claimed that it’s “hard to see how groceries” qualify as a perpetrator of “excessive” profits. A lesson in market concentration is overdue. Markets are ‘concentrated’ when a few companies control a substantial percentage of the market. Concentrated markets are not a consumer’s friend. At the consumer level, a 2023 USDA report revealed “[i]n most metropolitan areas, five to six store chains account for most supermarket sales.” The challenge here is that chains aren’t individually owned. For ex…