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Advantages Of Weak Form Efficiency

Satisfactory Essays

A Study of Empirical Tests of Weak-form Efficiency of Stock Markets
Sarika Mahajan

Key words: Efficiency, Stock Markets and Abnormal profits
JEL Classification: C18, G12, G14
Introduction:
The movement of stock prices is amongst few phenomenon that have cut across the boundaries of academic disciplines. These price movements are governed by rational, emotional, economical, geographical and psychological factors. The efficient market hypothesis (EMH) assumes that at any given time, security prices fully reflect all available information, which implies that price movements do not follow any pattern or trends. It further assumes that an efficient stock market must ensure rapid information access, so that it can instantaneously process the …show more content…

The EMH has historically been subdivided into three categories based on Roberts’ (1967) classical taxonomy of information sets:
 Weak form efficiency: Prices fully reflect historical information of past prices and re- turns.
 Semi-strong form efficiency: Prices fully reflect all information known to all market participants (public information).
 Strong form efficiency: Prices fully reflect all information known to any market partici- pant (public and private information).
For weak form tests, information can include past history of stock prices, company characteristics, market characteristics and the time of year. Tests for weak form market efficiency, more generally, referred to as tests of return predictability are discussed below:
1. Predictability of Past …show more content…

French (1980) studies daily returns on the Standard and Poor’s Index which is a composite portfolio of the 500 largest firms on the New York Stock Exchange over the period from 1953 to 1977. He found that the mean daily return on Monday during 1953-1977 is negative (-0.168%) and highly significant (t-statistic of - 6.82) while the average daily return on the other four days of the week are all positive. Moreover, the average daily return on Monday is also negative in each of the five- year sub-periods that were studied.
Various explanations have been proposed for the day-of-the-week effect. Lakonishok and Levi (1982) argue that the day-of-the-week effect is caused by the delay between trading and settlements in stocks and clearing checks. Accordingly, they adjusted the daily return on each day of the week during the period from July 1962 to December 1979 and found that the day-of-the-week effect is only partially eliminated. Therefore, the day-of-the-week effect can not be entirely accounted for by payment and clearing delays.

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