Concentration Ratio In economics, a ratio that indicates the relative size of firms in relation to their industry as a whole. Investopedia Says: The concentration ratio indicates whether an industry is comprised of a few large firms or many small firms. The four-firm concentration ratio, which consists of the market share (expressed as a percentage) of the four largest firms in an industry, is a commonly used concentration ratio. The Herfindahl index, another indicator of firm size, has a fair amount of correlation to the concentration ratio. Related Terms: Dog Eat Dog Economics Herfindahl-Hirschman Index - HHI Microeconomics Monopolistic Competition Monopoly Oligopoly Perfect Competition |