Concentration ratios and market definition
| English | Français |
|---|---|
| concentration ratio | concentration ratio |
| market definition | market definition |
A decision you can investigate
- Four brands may look like four competitors while one parent owns them all. A national share may hide a town with only one supplier.
- Define the market, measure and ownership before adding shares.
Build the explanation
- An n-firm concentration ratio 集中度比率 adds the market shares of the n largest independent firms in the defined market. Specify product, geography, period and share measure, such as sales value or physical volume. Rank firms rather than summing whichever n appear first in a table. A ratio describes the share held by the largest group, not how those firms behave. Higher concentration can suggest greater scope for market power or interdependence but does not establish collusion or a monopoly.
- Interpretation depends on entry barriers, import competition, substitutes, buyer power and ownership. Similar ratios can hide different distributions within the leading group. A merger can change concentration even with unchanged total sales; brand names should not be mistaken for independent decision makers. Broad national and narrow local definitions can yield different meaningful results, so justify the chosen scope.
Work through the evidence
- Fictional market sales shares are A30%, B25%, C15%, D10%, E8%, F7%, G5%, totaling100%. CR3=30+25+15=70%; CR4=80%. If E and F combine without changed sales, their share15% joins the leading group: the four largest become30,25,15,15 and CR4 rises to85%, not merely83%. A tie at third place does not affect this sum.
- Two separate markets can both have CR3=70%: one has30/25/15 for its leaders, another60/5/5. The same ratio conceals very different largest-firm shares. If total sales are200 and firm A sells60, its value share is60/200×100=30%; a volume-share calculation may differ when unit prices vary.
What is original CR3?
30+25+15=70.
Test the limits
- Do not add percentages with different denominators, years or geographies. Company groups may have overlapping sales requiring careful consolidation; count distinct transactions once. A narrow market definition 市场界定 can raise measured concentration, but it must reflect meaningful substitution, not a desired conclusion.
- Ratios omit potential entrants, efficiency, differentiated quality, conduct and future innovation. High concentration can coexist with strong potential-entry pressure; low concentration can coexist with coordination or local bottlenecks. Use the ratio as one piece of evidence alongside price-cost margins, entry/exit, customer alternatives and the costs of switching. The fictional figures are not current company statistics or legal thresholds.
What is CR4 after E/F combine under the assumptions?
Re-rank:30+25+15+15=85.
A high concentration ratio by itself proves that firms collude.
The ratio measures shares, not conduct or agreement.
Apply and explain your answer
- Why does merging E and F require re-ranking before calculating the new CR4?
- Their combined15% becomes one of the four largest firms and displaces the10% firm from the top-four sum.
Why can equal CR3 values describe different markets?
30/25/15 and60/5/5 both total70 but have different largest-firm shares.
Use the terms precisely
- concentration ratio: The combined share of the n largest independent firms in a defined market.
- market definition: The justified product, geographic and time scope used to identify competition.
Match the terms to their meanings.
Use each term for its stated economic relationship.
Fictional market sales shares are A30%, B25%, C15%, D10%, E8%, F7%, G5%, totaling100%. CR3=30+25+15=70%; CR4=80%. If E and F combine without changed sales, their share15% joins the leading group: the four largest become30,25,15,15 and CR4 rises to85%, not merely83%. A tie at third place does not affect this sum. Two separate markets can both have CR3=70%: one has30/25/15 for its leaders, another60/5/5. The same ratio conceals very different largest-firm shares. If total sales are200 and firm A sells60, its value share is60/200×100=30%; a volume-share calculation may differ when unit prices vary.
Do not add percentages with different denominators, years or geographies. Company groups may have overlapping sales requiring careful consolidation; count distinct transactions once. A narrow market definition can raise measured concentration, but it must reflect meaningful substitution, not a desired conclusion. Ratios omit potential entrants, efficiency, differentiated quality, conduct and future innovation. High concentration can coexist with strong potential-entry pressure; low concentration can coexist with coordination or local bottlenecks. Use the ratio as one piece of evidence alongside price-cost margins, entry/exit, customer alternatives and the costs of switching. The fictional figures are not current company statistics or legal thresholds.
An n-firm concentration ratio adds the market shares of the n largest independent firms in the defined market. Specify product, geography, period and share measure, such as sales value or physical volume. Rank firms rather than summing whichever n appear first in a table. A ratio describes the share held by the largest group, not how those firms behave. Higher concentration can suggest greater scope for market power or interdependence but does not establish collusion or a monopoly.