**7. Conclusions**

This paper reviews papers in the weak-form of market efficiency in the period between 1900 and 2019. Authors find that the results of the papers either support classical or adaptive nature of markets, indicating the EMH or AMH respectively. Extensive studies in return predictability have been conducted for testing the weak-form of market efficiency under both EMH and AMH. The weak-form of efficiency is also studied by testing the price–volume relationship under EMH, but in its adaptive form, very limited studies have been conducted by testing price–volume relationship. The literature lacks the studies in the price–volume relationship in the AMH domain. The adaptive market efficiency studies have been able to confirm that market efficiency is a dynamic concept and varies over time. This review leads to further scope in investigating the nonlinear cross–correlation between price and volume.

**Author Contributions:** This paper was conceptualized by A.C.P. A.C.P. also prepared the original draft including visualization. S.R. did the supervision and validation of the paper. Both the authors contributed in reviewing and editing. The software support was extended by A.C.P.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
