Trends in Aggregate Concentration in the United States
利用两个罕见数据集，测量了1980年代和1990年代美国总体集中度的变化，发现集中度在1980年代和1990年代初下降，1990年代末略有上升，但整体水平与1980年代末或1990年代初相当。
I assemble two rarely used data sets to measure aggregate concentration in the U.S. in the 1980s and 1990s. Despite the merger waves of those decades, aggregate concentration declined in the 1980s and the early 1990s, but rose modestly in the late 1990s. The levels at the end of the decade were at or below the levels of the late 1980s or early 1990s. The average size of firm and the relative importance of larger size classes of firms increased, however. Gini coefficients for employment and payroll shares of companies showed moderate but steady increases from 1988 through 1999.