Assessing private solutions to collective action problems in a 34-nation study

Collective action problems emerge when individual incentives and group interests are misaligned, as in the case of climate change. Individuals involved in collective action problems are often considered to have two options: contribute towards a public solution or free-ride. But they might also choose a third option of investing in a private solution such as local climate change adaptation. Here we introduce a collective action game featuring wealth inequality caused by luck or merit and both public and private solutions with participants from 34 countries. We show that the joint existence of wealth inequality and private solutions has a consistent effect across countries: participants endowed with higher income choose the private solution almost twice as often as those endowed with lower income; and this finding cannot be explained by different sources of wealth (luck vs. merit) or by cultural or economic factors. We also show that preferences for private solutions undermine support for public solutions, resulting in wealth inequality increasing in every country. In contrast, we identify two universal pathways to successful public solution provision: early contributions to public solutions and conditional cooperation. Our findings highlight the ubiquity of the ‘private solution problem’ and its potential consequences for global collective action problems.