Question 23

The four-firm concentration ratio is calculated by adding the market shares of the four largest firms.

This method provides a straightforward measure of market concentration, reflecting the total market share held by the top four firms in an industry.

A) By adding the market shares of the four largest firms

This option correctly describes the calculation of the four-firm concentration ratio. It involves summing the market shares of the largest four firms to determine the level of concentration in the market, which is a common practice in industrial organization.

B) By multiplying the squares of the market share of each firm

This option is incorrect as it describes a different metric known as the Herfindahl-Hirschman Index (HHI), which measures market concentration by summing the squares of the market shares of all firms, not just the four largest.

C) By adding the squares of the market share of each firm

This is also incorrect. While it pertains to the calculation for the Herfindahl-Hirschman Index, it does not reflect the methodology for calculating the four-firm concentration ratio, which simply adds the market shares of the largest firms.

D) By multiplying the market shares of the four largest firms

This option is incorrect because it describes a multiplicative approach that does not align with the method for calculating the four-firm concentration ratio, which requires an additive process rather than a product of the market shares.

Conclusion

The correct calculation of the four-firm concentration ratio is achieved by adding the market shares of the four largest firms, making option A the only accurate choice. All other options either pertain to different concentration measures or describe methods that do not apply to this specific calculation, thereby reinforcing option A as the definitive answer.