Final answer:
A four-firm concentration ratio is an indicator used in the field of business to measure the market share of the four largest firms in an industry. This ratio can help regulators assess the level of competition in an industry and determine the extent of monopoly power.
Step-by-step explanation:
A four-firm concentration ratio is an indicator used in the field of business to measure the market share of the four largest firms in an industry. In this case, the concentration ratio is 30 percent, which means that the combined market share of the top four firms in the industry accounts for 30 percent of the total industry sales. This ratio can help regulators assess the level of competition in an industry and determine the extent of monopoly power.