Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
This paper discusses alternative definitions of the terms "upstream" and "downstream," and shows how each can be represented within a single model of complementary oligopoly. The different definitions have strikingly different implications for the effect of vertical mergers. While the correct definition is not obvious, the model implies an observable condition that determines the competitive effect of a vertical merger. This condition can be a guide to empirical studies of vertical mergers and integration. Copyright 1989 by Blackwell Publishing Ltd.