Enforcement of contribution norms in public good games with heterogeneous populations

► We investigate the existence and emergence of contribution norms to public goods in heterogeneous groups. ► Uninvolved individuals hold well defined but conflicting normative views of fair contribution rules. ► Normatively fair contribution rules are related to efficiency, equality, and equity. ► In the experiment the efficiency norm and relative contribution norms are enforced, which differ across different types of heterogeneity.