Distinguishing among Competing Theories of the Market Share Effect
通过估计盈利能力的简化模型，发现市场份额系数不显著，表明市场份额对盈利能力的直接影响不存在，两者相关性主要源于未观测因素的共同影响。
Empirical studies assessing the role of market share in influencing profitability have been challenged because of their inability to distinguish among competing hypotheses. The author addresses this concern by estimating a reduced form model of profitability. The estimated reduced form, producing market share coefficients indistinguishable from zero, is consistent with an underlying structural model with no direct market share effect. The bivariate correlation between market share and ROI arises primarily from a failure to control for the unobservable factors contemporaneously influencing both variables and inducing serial correlation in ROI models. An alternative structural model that both contains a substantial market share effect and is consistent with the estimated reduced form is not apparent.