The world is increasingly characterized by transnational interdependence, cross-border policy externalities and the widely perceived need to provide certain global collective goods and to avoid global collective bads. Consider, for example, the problem of climate change and the need to limit greenhouse gas emissions; the problem of global refugee flows and the commitment to protect the human rights of forced migrants; and the problem of controlling and eradicating infectious diseases that can spread very fast, such as new forms of influenza. In all these cases, the need for “global governance”, that is, the challenge to make good collective decisions and to coordinate actions transnationally, is more pressing than ever. There are at least two dimensions of this challenge. First, global public goods are typically underprovided, and global public bads over-occur, in part because there are too few mechanisms to prevent free-riding at the global level (the “efficiency dimension”).1 And second, where global public goods are provided, and global public bads avoided, this is often the result of bargaining based on differential...