Two data sets were used in this research, labeled A and B. Sample A was constructed by starting with Schmalensee's sample of 1775 business-units from the 1975 file and appending data on the same business-units from the 1974, 1976, and 1977 files. After this expansion, one business-unit was judged to have unreliable asset measures (in 1976-77) and was dropped. Eight other observations were eliminated because assets were reported as zero. Sample A then contained 6932 observations provided by 457 corporations on 1774 business-units operating in a total of 242 4-digit FTC industries.