Suppose that a small town has seven burger shops whose respective shares of the local hamburger market are (as percentages of all hamburgers sold): 25 percent, 24 percent, 18 percent, 12 percent, 11 percent, 6 percent, and 4 percent.

a. Four-firm concentration ratio is the total sales percentage of the top 4 burger shops in the industry;

= 25% + 24% + 18% + 12%

= 79%

b. Herfindahl index is the sum of the squares of the percentage sales of all the shops in the industry;

= 25² + 24² + 18² + 12² + 11² + 6² + 4²

= ‭1,842‬

c. Top 3 shops combine to form one shop.

= 25 + 24 + 18

= 67%

Four-firm ratio = 67% + 12% + 11% + 6%

= 96%

‭Herfindahl index = 67² + 12² + 11² + 6² + 4²

= ‭4,806‬

answer; microeconomics;