Defining n;ki = 1 if corporation k has a business-unit in industry i in year t, and 0 otherwise, I adopt the notation that a 'dot' represents summation over the subscript normally in that position. For example, n;.1 is the total number of business-units reporting in industry i year t, and the total number of observations N = n. . .. With these preparations, the sample values of the sum-squares are