Heterogeneities within industries and structure-performance models

This paper tests whether the results from standard structure-conduct-performance [SCP] models estimated at the industry level are sensitive to the degree of heterogeneity of the firms in the industries. Industries are separated into homogeneous and heterogeneous categories depending on whether the profit rates of firms within an industry converge on a common value or not. In "homogeneous" industries we find that both the long-run projected returns on assets for the industries and Bureau of Census price-cost-margins are well explained by variables usually included in SCP models, as in particular industry concentration. In contrast, few if any of the usual SCP-model variables are statistically significant in the regressions for heterogeneous industries.