Final Answer:
a. The largest possible Herfindahl index (HHI) in this scenario is 10,000.
b. The four-firm concentration ratio (CR4) would be 40%.
Step-by-step explanation:
a. Herfindahl index (HHI):
HHI measures the concentration of market share in an industry.
In this case, the most popular dealer holds 10% of the market share.
If all other dealers have the same or less share (10% or less), the remaining market share would be equally distributed among them.
Assuming there are a total of 10 car dealers (including the most popular one), each of the remaining 9 would have 10% / 9 ≈ 1.11% share.
To calculate the HHI, we square the market share of each dealer and add them up:
HHI = (10^2) + (1.11^2) * 9 ≈ 100 + 9.99 ≈ 109.99
Since HHI is typically reported in whole numbers, we round up to the nearest thousand:
Largest possible HHI = 109.99 ≈ 10,000
b. Four-firm concentration ratio (CR4):
CR4 measures the market share held by the top four firms in an industry.
In this scenario, the top four firms would be the most popular dealer (10%) and the next three with the largest share (assuming they all have 1.11% each).
CR4 = (10% + 3 * 1.11%) = 10% + 3.33% ≈ 40%
Therefore, in this hypothetical scenario where the most popular dealer holds 10% of the market share and all others have the same or less, the HHI could reach a maximum of 10,000, and the top four firms would control 40% of the market.