Distinguish between different levels of market efficiency

The basic concept of levels of market efficiency was provided by Fama (1971), showing that market efficiency could be divided into three levels ranging from weak to strong form. Firstly, the weak form argued that stock prices reflect all historical trading information in terms of trading prices, volume or interest (Baiz et al,1999). Thirdly, in the strong form, share prices fully and fairly reflect all information including historical, publicly available information and insider information.