THE EVOLUTION OF STOCK MARKET EFFICIENCY OVER TIME: A SURVEY OF THE EMPIRICAL LITERATURE
Kian-Ping Lim
Universiti Malaysia Sabah and Monash University and Robert Brooks
Monash University

Background
This paper provides an insight into the empirical literature as pertains the evolution of stock market efficiency over time, with a keen focus on the weak form Efficient Market Hypothesis (EMH). The authors provide a systematic review of the correlation between several financial factors namely: Adaptive Markets Hypothesis (AMH), Efficient Markets Hypothesis (EMH), Evolving Return Predictability, Stock markets and Weak-form EMH. The authors pay keen attention on how return predictability from past price changes is affected by key players and determinants on the stock markets. From the survey they conduct, the posit that the bulk of the empirical studies examine whether the stock market under study is or is not weak-form efficient in the absolute sense, assuming that the level of market efficiency remains unchanged throughout the estimation period.

The authors acknowledge that one field that has drawn extensive investigation by scholars and other players alike is the predictability of stock returns on the basis of past price changes. This is partly due to its direct implication on weak-form market efficiency. They find that a vast majority of the literature implicitly assumes the level of market efficiency remains unchanged throughout the estimation period. However, the possibility of temporal instability in the underlying economic relations has received increasing attention from economists (see, for example, Stock and Watson, 2003).

Kian-Ping Lim and Robert Brooks through their present survey show that there is an expanding literature which challenges the assumed static characteristic of market efficiency by means of non-overlapping sub-period analysis,