The behaviorists argue that the reason we’re rejecting the joint hypothesis of market efficiency and CAPM is that markets aren’t efficient because behavioral biases exist (see section 9.4 on that)....

The behaviorists argue that the reason we’re rejecting the joint hypothesis of market efficiency and CAPM is that markets aren’t efficient because behavioral biases exist (see section 9.4 on that). Shiller said that Fama is known as the father of the modern efficient markets theory. In contrast, he has argued that the theory makes little sense, except in fairly trivial ways.