N this paper I investigate proposition that price-cost margin of a producer goods industry will vary systematically with what I call industry's importance of its output in costs of its industrial customers. The empirical results indicate that price-cost margins are indeed negatively associated with cost-importance, particularly in highly concentrated industries. In these industries at least, evidence seems to confirm the importance of being unimportant. In section I, I present relationship between derived demand elasticity for an industry's output and cost-importance of its output, and also analyze ways in which industry pricing coordination and transaction costs of changing input suppliers interact with cost-importance to influence industry price-cost margins. In sections II and III I describe process of sample selection and a method for calculating a measure of cost-importance for producer goods industries. In section IV I present empirical results of estimating relation between price-cost margins and cost-importance for a broad sample of producer goods industries, and in section V I summarize my findings and suggest some promising avenues for future research.

JN the thirty years since Joe Bain's seminal I study (1951), many economists have attempted to determine whether or not there exists a critical level of market concentration at which a discontinuity occurs in the relation between industry concentration and profitability. In this paper we develop and test a more general model, based on organizational costs, which posits the existence of two critical levels of market concentration: one at which an existing cooperative equilibrium will break down as concentration declines, and one at which a cooperative equilibrium will become attainable as concentration increases. We show that the standard model of the critical level of concentration can be regarded as a special case of our more general model, and also that the more general model attains a statistically superior fit. In section II we briefly review some of the previous literature in this area. We develop our model in section III and specify and estimate it in sections IV and V. In sections VI and VII we summarize and interpret our results and present some policy implications of our findings.

EVERYBODY talks about the relation of industries' profit rates to their markets' rates of growth, but nobody does anything about it. Specifically, researchers have confirmed the effect of the growth of nominal output on profits in many multivariate studies, without specifying closely the hypothesis under test or the measure of demand growth appropriate to test it. A profits-growth relationship could stem from several mechanisms-the lagged adaptation of capacity to unexpected changes in demand, reactions of oligopolists to disturbances in their consensus, etc. These mechanisms-how and where they work-hold their own normative interest. Therefore, knowing what behavior (and what structure, lying behind it) accounts for the profits-growth relationship should do more than improve the specifications of our studies of allocative efficiency. It should also expand our knowledge of adaptive processes that are important and hard to observe directly. In this paper we shall synthesize the available explanations of why changes in market demand should affect an industry's profits, then present a statistical test of the relative significance of the competing explanations.