Three of them for having won (highly deservedly) the Nobel prize and one for having been a beacon of light and guidance during the latest crisis. Many would have thought that his increasingly public role--and contempt for everything Republican--in recent years had diminished his chances, but the committee made the right choice. Paul's contributions to international economics are legion. His ability to cut to the heart of the matter with just a couple of equations is unparalleled in the profession.
Some years ago I was at a Festschrift conference for Jagdish Bhagwati at Columbia--Paul's teacher at MIT and himself a frequently mentioned name in connection with the Nobel prize. One of the speakers was Paul Samuelson. Now the usual drill on such occasions is to toast the man of the moment with a combination of wit and eloquence. I don't recall if Samuelson even mentioned Bhagwati. What I recall is that Samuelson spent his whole time on a detailed exegesis of Paul's work on trade. I should have known then that if the Nobel committee were to give another prize in international trade, it would go to Krugman.