The extent of single firm dominance in U.S. manufacturing industries

This paper presents upper and lower bound estimates of leading firm market shares in U.S. manufacturing industries, and of the ratio of leading firm shares to the combined shares of the next three largest firms. These estimates suggest that extreme dominance is not a common feature of the U.S. industrial landscape, although unequal share distribution among leading firms is common. Dominance appears to be an important cause of differences among industries in four-firm concentration ratios. Finally, single firm dominance might account for as much as 16% of observed concentration levels.