 "The Guardian" ranked "The Tipping Point" #94 in its list of 100 Best Books of the 21st Century.Some of Gladwell's analysis as to why the phenomenon of the "tipping point" occurs (particularly in relation to his idea of the "law of the few") and its unpredictable elements is based on the 1967 small-world experiment by social psychologist Stanley Milgram.Milgram distributed letters to 160 students in Nebraska, with instructions that they be sent to a stockbroker in Boston (not personally known to them) by passing the letters to anyone else that they believed to be socially closer to the target.