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WHAT HAS BEEN HAPPENING TO AGGREGATE CONCENTRATION IN THE U.S. ECONOMY IN THE TWENTY‐FIRST CENTURY?

This paper extends earlier data series on aggregate concentration in the U.S. economy—the percentage of aggregate economic activity that could be attributed to the largest “X” companies—into the first two decades of the twenty‐first century. We find that there has been a moderate but continued increase in aggregate concentration since the mid‐1990s. This increase appears in data on employment and payrolls that have been compiled by the U.S. Bureau of the Census, as well as employment and profits data that are drawn from the annual “Fortune 500” lists. This increase does not, however, appear to have raised aggregate concentration above the levels of the early 1980s. (JEL L10, L11, L19)