Beyond the efficient markets hypothesis: Towards a new paradigm

To go beyond the efficient markets hypothesis (EMH) we suppose that the stock market can be in one of three states: (1) a fundamental state, where share prices are determined largely as in the EMH; (2) a bubble or bull market state, where share prices are above their fundamental levels but are expected to continue to rise further, and (3) a bear market state, where shares are held exclusively by irrational agents and rational agents cannot exploit the overvaluation because of short‐selling constraints. Also, heterogeneous rational expectations may help explain some features of stock market behaviour.