Explanation

Both the concentration ratio and the Herfindahl-Hirschman Index (HHI) are measures of market concentration that focus on existing firms in an industry. They do not consider the possibility of new entrants.

Key Points:

1. Concentration Ratio: Measures the percentage of market share held by the largest N firms (typically 4 or 8 firms). It only looks at current market participants.

2. Herfindahl-Hirschman Index (HHI): Calculated by summing the squares of the market shares of all firms in the industry. Like the concentration ratio, it only considers existing firms.

3. New Entrants: The threat of new entrants is part of Porter's Five Forces analysis, which examines competitive forces in an industry. This is a qualitative assessment, not captured by quantitative concentration measures.

4. Limitations of Concentration Measures: Both CR and HHI have limitations:

   • They don't account for potential competition
   • They don't consider geographic market boundaries
   • They don't account for product differentiation
   • They assume market shares accurately reflect competitive pressure

Therefore, the correct answer is C - neither measure considers the possibility of new entrants.