IN a recent issue of this Journal, Lawrence White [4] claims to show that aggregate concentration has not increased in the U.S. economy over the past two decades; hence, whether or not high levels of aggregate concentration represent a problem for society, this "problem" has at least not gotten any worse (despite numerous conglomerate mergers during the period). However, I disagree with his conclusion; an alternate measure to that used by White shows that aggregate concentration in manufacturing has steadily, though slowly, increased over the entire post-war period. While the shares of value-added controlled by the largest 50, 100 or 200 manufacturing firms (CR50, CR100, CR200, respectively) have remained roughly constant since the early 1960s, the number of firms has increased, implying that value-added has become less evenly distributed across manufacturing firms. Similarly, aggregate concentration in the entire private sector can be seen to have increased during the 1970s when the distribution of after-tax income is examined.