Final answer:
The question does not match the multiple-choice options, but commonly, the four-firm concentration ratio and Herfindahl-Hirschman Index (HHI) are used to analyze market shares and competition.
Step-by-step explanation:
The most common method used to calculate the market share and market size variances is not explicitly provided in the multiple-choice options. However, commonly used techniques to measure the extent of competition and market share include the four-firm concentration ratio and the Herfindahl-Hirschman Index (HHI). The four-firm concentration ratio is calculated by adding the market shares (as a percentage of total sales) of the four largest firms in the market. The HHI is calculated by taking the market shares of all firms, squaring them, and then summing the total. While these methods do not directly answer the student's question, they provide insight into common practices for analyzing market dynamics.
For example, let's say a company's sales revenue is $1 million, and the total market sales revenue is $10 million. The market share would be calculated as:
Market Share = (1,000,000 / 10,000,000) * 100 = 10%.