The determinants of market share for the `dominant firm' in telecommunications

The present study examines the factors affecting the market share of the dominant firm in long-distance telecommunications, AT&T. A theoretical model is specified which includes competing long-distance rates (e.g., those of MCI and U.S. Sprint), price-cap regulation and advertising expenditures as determinants of the dominant firm's market share. Using intercity long-distance carrier charges for 1984–1994, this study points out the importance of AT&T's own rate structure, those of its major competitors, and government regulations in determining AT&T's market share over time.