Measuring Common Ownership : The Role of Blockholders and Insiders

We construct and analyze a new data set on U.S. corporate ownership to study how the inclusion of blockholders' and corporate insiders' holdings affects the measurement of common ownership among America's largest publicly traded firms. Including blockholders’ and insiders’ holdings reveals that (i) the level of common ownership is lower than previously believed, (ii) its variation is higher in some subsamples of the data and lower in others, (iii) investor concentration is much higher and more variable. Further, (iv) the ``Big 3'' asset management firms' holdings positively contribute to common ownership, overturning previous findings based on ``passive'' institutional ownership alone