A market anomaly (or market inefficiency) is a price and/or rate of return distortion/bias on a financial market that seems to contradict the efficient-market hypothesis, as conceived by Fama (1970) in his seminal paper.
There are a lot of market inefficiencies in the financial markets, and particularly, they are of three kinds:
- Calendar effects;
- Structural biases;
- Behavioural biases;