Tradable Immigration Quotas
International migration is maybe the single most effective way to alleviate poverty at a global level. When a given host country allows more immigrants in, this creates costs and benefits for that particular country as well as a positive externality for all those (individuals and governments) who care about world poverty. This implies that the existing international migration regime is inefficient as it fails to internalize such externality. In addition, host countries quite often restrict immigration due to its apparently unbearable social and political costs. However these costs are never measured and made comparable across countries.