We study the evolution of profits, investment, and market shares in US industries over the past 40 years. During the 1990s, and at low levels of initial concentration, we find evidence of efficient concentration driven by tougher price competition, intangible investment, and increasing productivity of leaders. After 2000, however, the evidence suggests inefficient concentration, decreasing competition, and increasing barriers to entry as leaders become more entrenched and concentration is associated with lower investment, higher prices, and lower productivity growth.

中文翻译：

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从好到坏的浓度？过去 30 年的美国工业

我们研究了过去 40 年美国工业的利润、投资和市场份额的演变。在 1990 年代，在初始集中度较低的情况下，我们发现了由更激烈的价格竞争、无形投资和领导者生产力提高驱动的有效集中度的证据。然而，在 2000 年之后，有证据表明，随着领导者变得更加根深蒂固，并且集中度与投资减少、价格上涨和生产率增长放缓有关，导致效率低下、竞争减少、进入壁垒增加。