Fair Trade Law Q&A - Market Definition and Market Share Calculation

How is market share calculated after the relevant market has been defined?

To measure market share, it is necessary first to define the relevant market; then, identify the firms participating in that market, select an appropriate period of time (typically one year), and adopt an appropriate metric - such as sales value, output, production capacity, or reserves - to measure the size of the firms or the market.

Market share is thus calculated by determining the ratio of an individual firm's sales volume, sales value, or other relevant variables within the relevant market during the specified period (excluding exports) to the total sales volume or sales value of all suppliers in the relevant market during the same period. This ratio constitutes the firm's market share.