An excerpt from my most recent edition of Trend Following:
Trend following is as much about observing and understanding human behavior as it is about moving averages, breakouts, and position sizing. Understanding human behavior and how it relates with markets is commonly referred to as behavioral economics or behavioral finance. It evolved from the contradiction between classical economic theory (EMT) and reality. The assumption people act rationally, have identical values and access to information, and use rational decision making is one preposterous assumption.
However, trend following strategies only work if price trends continue. But why should trends continue? If prices initially under-react to either good or bad news, trends tend to continue as prices slowly move to fully reflect changes in fundamental value. These trends have the potential to continue even further as investors herd (or chase trends). Herding can cause prices to overreact and move beyond fundamental value after the initial under-reaction. Naturally, all trends must eventually end, as deviation from fair value cannot continue infinitely. Said another way, people are irrational as hell and seldom make rational decisions even if they think they do. That’s not my one-man opinion either. I have had the good fortune to learn from and interview the top minds in the field of behavioral economics and finance, including Nobel Prize winners Daniel Kahneman and Vernon Smith, Dan Ariely, Colin Camerer, Christopher Chabris, Robert Cialdini, K. Anders Ericsson, Gerd Gigerenzer, Donald MacKenzie, Spyros Makridakis, Terrance Odean, Steven Pinker, Laurie Santos, Hersh Shefrin, Daniel Simons, Paul Slovic, Didier Sornette, Meir Statman, Brett Steenbarger, and Philip Tetlock to name a few of the best minds in the field. (You can find these interviews on my podcast at www.trendfollowing.com/behavior.)
Some want to argue about everything but this. Big mistake.