Internet portals serve as platforms for coordinating advertisements, content, and user markets. We model portal structure with South Korean market data to explain network effects and other competition factors. We also analyze network effects on profit and market efficiency. The results indicate a negative network effect from banner advertisements in the user market, which is countered by a network effect from content provision. In the advertising market, the network effect from user demand is positively identified, which explains profit making through increased user visits. Furthermore, we show that network effects due to market concentration result in increases in consumer surplus.

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Organizational behavior theories can be subject to potential inversions in the nature of the effects expected or described (i.e. an effect inverts from positive to negative or vice versa). Yet, inversions are rarely considered or assessed. We explore three possible canonical inversions: the maximum or minimum point in a quadratic regression model, the point of intersection in disordinal interactions, and the change of slope in a moderated regression model. We describe both the motivation for, and the theoretical and empirical importance of, considering such inversions in theory-building and testing. We consider common situations in which inversions are misinterpreted empirically and present methods to conduct explorations for potential inversions. Two different cases of errors concerning inversions can occur. In the first case entailing omission, an inversion is occurring but is not observed in the sample. In the second case, researchers wrongly assume an inversion is occurring in their model, yet the prospective inversion would actually occur out of the range of possible values on the focal variable(s), and is thus not significant. We illustrate different types of inversions using simulated examples. Ultimately, we seek to encourage and equip management researchers to identify important theoretical boundary conditions imposed by inversions. slope of the moderated regression line crosses zero (inverts) and thus the simple slope changes sign. Setting the simple slope to zero and solving for M gives the value of the inversion point: 938F. L. CAVARRETTA ET AL.