Consider data on U.S. Pizza Sales from 2005. The market shares of the top 4 firms was 17% for Pizza Hut, 11% for Domino’s, 6% for Papa John’s, and 2.5% for Little Caesars. Firms 5 through 25 combined summed to 14.5%, and all other independents outside the top 25 selling firms comprised the other 50% of industry sales.
What is the 4-firm concentration ratio for this industry?