Thanks Daniel. Here are the two studies I mentioned: The one about Fiji is by me and Satish Chand. There's a video of me presenting it at Stanford, here: http://www.cgdev.org/content/multimedia/detail/1424969 ...and the paper is here: http://www.cgdev.org/content/publications/detail/123641/ The paper on Cape Verde is not mine, it's by Batista, Lacuesta, and Vicente, forthcoming JDE, available here: http://www.pedrovicente.org/brain.pdf I didn't espouse any moral absolutes at all in my comment. I said that the right to emigrate is well-established, so if policy is going to curtail that right (i.e. moving away from absolutes) then there should be good reasons for it, which is sensible. And giving good reasons means we need answers to many questions. I didn't say we have those answers (again, no absolutes). I said that we don't have the answers we need in order to feel fine doing definite harm to people by restricting their choices in seeking a better life. I do not think there is a good answer to the question of who owns the positive externalities you convey to other people. I do think that it's not obvious that other people own them. I also think that if society is going to give even partial ownership of your positive externalities to other people, then it also makes sense to give other people partial ownership in your negative externalities as well, so that if you do anything bad to another person, society should be partially punished. Since that state of affairs is something that strikes me as unjust, that makes me question the idea that other people should hold even a partial property right in your externalities -- negative or positive. None of this is absolutist; I'm asking for reasons to change my views. But I don't now see any.