Can prices already reflect all information

Explain the Efficient Markets Hypothesis and its different forms.

EMH states that prices already reflect available information, so it is impossible to earn excess risk-adjusted returns consistently. The weak form covers past prices (technical analysis fails), the semi-strong form all public information (fundamental analysis fails), and the strong form includes private information. Evidence for anomalies, bubbles and behavioural biases challenges it, yet it remains a useful default that edges are small and hard to keep.