What is Efficient Market Hypothesis?
The efficient market hypothesis (EMH) states that asset prices fully reflect all available information, so it is impossible to consistently earn returns above the market on a risk-adjusted basis. EMH comes in three forms: weak, semi-strong and strong, depending on which information is already priced in.
How It Works
- Weak form: prices reflect all past price and volume data.
- Semi-strong form: prices also reflect all publicly available information.
- Strong form: prices reflect public and private information.
- Each stronger form rules out a wider set of strategies for beating the market.
Saudi Context
Capital Market Authority disclosure rules in Saudi Arabia aim to push the Tadawul market closer to semi-strong efficiency by ensuring material information reaches all investors at the same time.
Example
Under semi-strong EMH, by the time you read a Saudi listed company’s earnings release on Tadawul, the share price has already moved to incorporate it.