There are various forms of market efficiency which, however, only discriminate on the degree
of efficiency similar to how economists describe how perfect a market is: perfect or imperfect etc.
Nevertheless, in the literature reference is made to three types of EMH, the strong form (markets very
efficient), semi-strong and weak (markets not very efficient). A strongly efficient market would be one
in which security prices fully reflect all available information – and do so immediately the information
becomes available – all new information is immediately absorbed by the market. A leading figure in
the development of the EMH in finance, Eugene Fama, states that a market is efficient if “security
prices fully reflect all available information” (1970, p 384). It should be noted that available
information will include all information that investors use to make investment decisions and
accounting will only be a part of such information.