This is fascinating:
Between 1946 and 1954 in the U.S., the share of food bought in supermarkets rose from 28 percent to 48 percent. By 1963, that number had risen to nearly 70 percent. A&P had so much market power that the Department of Justice went after it for anticompetitive practices. This was an interesting development, considering that the U.S. Government played such a significant role in the creation of supermarkets in the first place.