The Greater Fool Theory

The greater fool theory posits that rational people will buy into valuations that they don’t necessarily believe, as long as they believe there is someone else more foolish who will buy it for an even higher value. The human tendencies described above lead to a fairly predictable outcome: After an innovation is introduced and a market is formed, people believe both that they are among the few who have spotted the trend early, and that they will be smart enough to pull out at the right time.