4. (Ch.13) Measuring industry concentration or market power using the four-firm concentration ratio (CR₄) and the Herfindahl Index (HHI).

The data below gives the percentage of total sales for each firm in industries a through f. Calculate the CR₄ and HHI.

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Market share (%) CR₄ (%) for the HHI HHI

a. 100% (1 firm) _______ ___________________ _______

b. 70%, 30% (2 firms) _______ ___________________ _______

c. 50%, 25%, 15%, 10% _______ ___________________ _______

d. 25%, 25%, 25%, 25% _______ ___________________ _______

e. 25%, 25%, 20%, 20%, 10% _______ ___________________ _______

f. 100 firms with equal market shares _______ ___________________ _______