Price Leadership and Dynamic Aspects of Oligopoly in U.S. Manufacturing
基于314个四位数制造业行业的数据，发现集中度随生产率上升而增加主要发生在低集中度行业，而集中度随生产率上升而下降主要发生在高集中度行业，间接支持了少数大企业先推动生产率提升和集中化、随后小企业模仿导致集中度下降的假说。
This study, which covers a sample of 314 four-digit industries taken from an exhaustive set of 450 four-digit industries, shows that increases in concentration associated with rising productivity occur mainly in low-concentration industries, while decreases in concentration associated with rising productivity occur mainly in high concentration industries. The empirical results of this study indirectly lend support to a plausible hypothesis that a small group of firms makes a big impact on the productivity of an initially unconcentrated industry and thereby concentrates it. Later, the small firms imitate the now big firms, and concentration goes down while productivity keeps rising.