DIFFERENTIAL INTERESTS, EQUITY, AND PUBLIC GOOD PROVISION

This study examined the effect of differential interests on public-good provision. In fictitious four-person groups, two members benefitted more from the public good than the others. Subjects were either in a High-Interest position (receiving 33% of the public good) or in a Low-Interest position (receiving 17%). In order to investigate whether equity theory may provide an adequate explanation for the effect of the interest differentials, we manipulated the justification of the interest differences. These differences were either justified (by an asymmetry of inputs) or not justified (because of symmetry of inputs). This setup provided a 2 (Interest: High, Low) × 2 (Justification: Justified, Not Justified) factorial design. Predictions on the basis of equity theory were largely confirmed. The subjects were more motivated to minimize differences in final outcomes when Interest differentials were Not Justified than in case of a Justified distribution. On a behavioral level, High-Interest subjects contributed more than Low-Interest subjects when the interest distribution was Not Justified, but no differences were found in case of a Justified distribution. In addition, the results indicated the usefulness of distinguishing two contribution rules: the equal contribution rule and the proportional contribution rule. The proportional contribution rule was preferred in the Not Justified conditions. No differences were found in the Justified conditions. © 1993 Academic Press. All rights reserved.