When
investors or individuals put money into the stock market, their goal is to
receive a return on the capital invested. Many investors try not only to make a
profitable return, but also want to outperform or beat the stock market. For
this situation, Eugene Fama suggests that at any given time, prices fully
reflect all available information on a particular stock and no investor has an
advantage in predicting a return on a stock price because no one has access to
information not already available to everyone else.
Many
financial researches recognize that the financial markets are informationally
efficient as the market prices fully show publicly available information. But
the market may not attain such efficiency when publicly available information
is costly to produce and when investors can always purchase better information
at a higher price. While, when investors stop to buying information and trade
shares, the amount of information purchased by the public and the quality of
information reflected in the market price can be endogenous. Therefore, market
efficiency relies on the cost structure of producing information, investors’
behaviors and risky return.
Market
efficiency does not require prices to be equal to fair value all the time.
Generally, stock prices would be over or lower than the actual prices but
eventually revert back to their mean values. This is because the deviations
form a stock’s fair prices are in themselves random, investment strategies that
result in beating the market cannot be consistent phenomena. Furthermore, the
hypothesis argues that an investor who outperforms the market does so not out
of skill but out of luck. However, we cannot deny that
in the real world of investment, there exists investors that have beaten the
market, for instance, Warren Buffet, whose investment strategy focuses on
undervalued stocks, made millions and set an example for numerous followers.
There
are three levels of efficiency, weak form efficiency, semi strong form
efficiency and strong form efficiency, which are used to reflect in prices and
to define whether the market is efficiency. For weak form efficiency, share
prices fully reflect all information contained in past price movements. But it
is useless for investors to gain profit based on share price history. Semi
strong form efficiency, share price indicates all the relevant publicly
available information, which implies that there is no advantage in analyzing
publicly available information after it has been released, because the market
has already absorbed it into the price, therefore, investors technical analysis
cannot result in profits but internal information may bring in profits. Strong
form efficiency, all relevant information, including that which is privately
held, is reflected in the share price. In this market, even insiders are unable
to make abnormal profits for investors.
Take
the HP acquired Autonomy as an example. The US stock market can be considered
in the level of semi strong form efficiency market. As the management overprice the Autonomy's share price, HP made a $8.8 billion loss after 15 months of the acquisition.This is owing to the fact that Autonomy has inflated in their accounting data, which belongs to a insider information. If the HP's managers has discovered the forge before the acquisition, they would not overprice the share price and result in great losses.
It is
important for the market to be efficient. Because a more efficient market
encourages individuals invest in private enterprise. If shares are incorrectly
priced many savers will refuse to invest because of a fear that when they come
to sell the price may be perverse and may not represent the fundamental
attractions of the firm. Secondly, as the object of one company is to create
shareholders value, this provides a signal for company managers to make a sound
decision. In addition, share prices signal the rate of return investors demand
on securities of a particular risk level. If the market is inefficient the risk
return relationship will be unreliable so that managers might misestimate the
price, leading to excessive high cost capital. Thirdly, valuation of the stock
market helps the company allocate resources, including operating efficiency and
pricing efficiency.