A market share is the percentage of total sales completed by a company within an industry in a specific time period, typically one year. Market shares show the size of the company in that specific industry. Studying the market shares of an industry are important in order to understand the type of competition that the companies in that industry are facing.
To evaluate the competition in an industry, you can calculate two indexes: the n-firm concentration ratio and the Herfindahl index, which you will also use later to categorise industry types. Before starting your analysis, remember that if a company operates in more than one industry, it is very important to distinguish which revenue stream corresponds to the analysed industry.