Why do citizens in some countries take more responsibility for the well-being of others than in other countries? This project seeks to understand the genesis of prosociality, investigating its biological foundations, the influence of cultural traditions, and e ects of political, economic and legal structure. The dominant theory in economics views philanthropy as a solution to social illnesses that the market and the state are not solving, a view complementary to political science theory on preferences for government provision. Sociologists focus on social norms emerging from religious traditions. Cultural evolutionary theory highlights the instrumental value of trust. Still other theories have suggested a role for natural selection of genes. However, these theories have not been tested stringently nor simultaneously. Also the project includes a very important factor largely ignored thus far: political, legal and economic institutions also a ect the level of giving as well as who gives to which causes. Therefore, the objectives of Global Giving are (1) to map country di erences in the size and nature of philanthropy across the world; (2) to develop and test multidisciplinary theories explaining these di erences; (3) to facilitate international collaboration across disciplinary boundaries in research on philanthropy. The research draws upon 200 surveys recently harmonized by the PI and on new data on philanthropy to be collected among large samples in 145 countries across all continents. Collaboration with international networks of academics safeguards the validity of the questionnaires and experiments. Appropriate multilevel regression models will be used, the lack of which caused biases in previous research. An integrated understanding of philanthropy is useful not only for theory development, but also for government policy makers and practitioners in nonprofit organizations seeking to mobilize philanthropic contributions and make them more e ective. The application in practice is ensured through collaboration with a large network of practitioners.