All of the following are considered to be problems associated with the use of concentration ratios to measure market power except:
A) two different markets with the same concentration ratio may have very different distributions of market share among firms used to calculate the concentration ratio.
B) concentration ratios are often based on national statistics and may not reflect substantial concentration in a market at a more localized level.
C) the market definitions used in their construction may be arbitrary.
D) consideration of exports and imports generally causes concentration ratios to be overstated.