Ideals should not be too ideal: Identity and public good contribution

This paper incorporates identity into a model of voluntary public good contribution. An ideal of contributing to public goods divides players to di¤erent social categories: Players who identify with the ideal become insiders, obtaining identity utility but incurring disu- tility if their contributions depart from the ideal, while players who do not identify with the ideal remain as outsiders. We show that identity could increase public good contribution; the ideal that best resolves the free-riding problem in the public good game equals either the contribution level of the most altruistic player in the absence of the identity, or a level that makes the least altruistic player indi¤erent between becoming an insider and not, depending on the size of the group. These results have implications for social policymaking.