The last one is Post Earnings Announcement Price Drift. For an efficiency market the price
of stock should reflect the information immediately after the release, however, what in
reality is that price continued to rise or fall through a period after the announcement date
and so was the abnormal returns . It is called Post Earning Announcement Drift.
The last test is inside information. In a case that insiders make big return because of
knowing the inside information, the market is said to be inefficient . As the price of stock
is not fully reflect all the available information.
Besides, for all the tests above, there is one common problem related to the tests. That is,
as the test conducted by using risk models, it may then need to take into account of the
efficiency of the models used .
PART 2
A market anomaly exists where findings cannot be reconciled with the efficient market
hypothesis or when returns when risk adjusted are still abnormal. Prior to examining the
anomalies in the US and Australian markets, it is necessary to examine the different forms
of market efficiency, rendering the violation of specific anomalies to the level of market
efficiency. The weak form of market efficiency maintains that all current prices reflect all
past information, including information derived from technical analysis, history of prices,
trading volumes or short term interest rates. The semi-strong form hypothesis maintains
that all publicly available information should already be impounded into the stock price;
this would obviously include everything that is known about the firm, eg, product line, and
earning forecasts made should reflect in current prices. Strong form efficient hypothesis
asserts that all information, including insider information should be impounded into stock
prices. Thus if markets are efficient, then only new information should affect the future
movement of prices, and since new information is unpredictable , prices should follow a
random walk – that is, they are equally likely to move up or down.
There are five prominent market anomalies highlighted in past research for US markets.
1. Momentum and reversal Effects anomaly also known as the winner-loser anomaly
Momentum effects are observed, where in the short horizon of typically less than three
months, stock that perform well continue to perform well, while stocks performing poorly
continuing to perform poorly. Thus in the short horizon, stock prices exhibit a positive
serial correlation. Serial correlation refers to a tendency for future performance to be
related to the past. Here the price of stock can be (weakly) predicted based on the last