What is Random Walk Theory?
A Random Walk Down Wall Street, written by Burton Malkiel in 1973, has become a classic in
investment literature. Random walk theory jibes with the semi-strong efficient hypothesis in its
assertion that it is impossible to outperform the market on a consistent basis. Malkiel puts both
technical analysis and fundamental analysis to the test and reasons that both are largely a waste
of time. In fact, he goes to great lengths to show that there is no proof to suggest that either
can consistently outperform the market. Any success outperforming the market with technical analysis
or fundamental analysis can be attributed to lady luck. If enough people try, some are bound to
outperform the market, but most are still likely to underperform.
The basic random walk premise is that price movements are totally random. Judging from the chart,
the price movements of Newmont Mining over this 5-month period would appear to be quite random.
Prices have no memory, therefore past and present prices cannot be used to predict future prices
(as implied in technical analysis). Prices move at random and adjust to new information as it comes
available. The adjustment to this new information is so fast that it is impossible to profit from
it. Furthermore, news and events are also random and trying to predict these (fundamental analysis)
is also a lesson in futility.
Malkiel maintains that a buy and hold strategy is best and individuals should not attempt to time
(or beat) the market. Attempts based on technical, fundamental or any other analysis are futile.
Admittedly, he does have a point. Statistics have shown that the majority of equity mutual funds
fail to outperform the market, as measured by the S&P 500. Investors can easily buy index-based
securities with very low transactions costs.
Should random walkers take a hike?
While there are some good points to be gleaned from the random walk theory, it appears to be a bit
dated and does not accurately reflect the current investment climate.
Random walk theory was introduced over 25 years ago when institutions dominated the market. These
institutions had superior access to resources and the individual was at the mercy of the large
brokerage houses for quality research. With the advent of online trading, power and influence are
shifting from institutions to the individual. Resources are now widely available to all at minimal
cost, if not free. Not only can individuals access information, but the Internet ensures that
everyone will receive it almost instantaneously. They also have access to real time data and can
trade like the pros. With the availability of real time data and almost instant executions,
individuals can act on information like never before.
As little as 5 years ago, transactions costs were high and figured into any investment or trading
strategy. Again, with the advent of online trading, transactions costs have become minimal. This
has increased the amount of trading volume and probably volatility. Higher volatility increases the
possibility that anomalies will develop. With better trading resources and low commissions, more
traders and investors than ever are able to capitalize on potential anomalies.
For obvious reasons, the Wall Street establishment is not thrilled about random walk theory. After
all, Wall Street is in the business of analysis, strategy and money management. However, it is a fact
that about 75% of equity mutual funds underperform the S&P 500 year after year. Some of this
underperformance can be blamed on transaction costs and management fees. However, with the advent of
index-linked securities, the onus will be on the money managers to figure out a way to outperform
the market, or lose business.
In truth, 75% of equity mutual funds underperforming is not as bad as it sounds. When the Random Walk
theory was introduced in 1973, or even 15 years ago, around 90% of equity mutual funds underperformed
the market. Since this number seems to have risen, it would appear that either stock picking is getting
better or fees are getting smaller, or both. 15 years ago, the stock market and mutual funds were much
more homogeneous. Even though there were tech stocks, they did not exert nearly as much influence. With
the explosion of the NASDAQ, tech stocks play a much larger role in today's market. Internet stocks,
which have also come to the forefront, did not even exist 15 years ago. With an increase in specialty
mutual funds catering to tech and Internet, the total number of mutual funds has proliferated over the
last few years. With the increase in mutual funds has also come an increase in the diversity of such funds.
There are funds for almost every sector, industry or index imaginable and investors have a wide array of
choices. The more homogeneous mutual funds there are, the less chance there is to outperform. However,
this specialization has created a hierarchy among mutual funds and helped to increase the percentage
funds that outperform the S&P 500 from 10% to 25%.
History has proved that a buy and hold strategy outperforms most attempts to time the market in
absolute returns. In risk-adjusted returns, the argument loses some of its credibility. Buy and hold
may take the guesswork out of beating the market, but it does little to compensate for the risk
associated with a continuous investment in the market. There is a direct correlation with risk and
return: the higher the expected return, the higher the associated risk. A portfolio with a timing
strategy that seeks to move into risk-free treasuries when a bear market is signaled (Dow Theory for
example), significantly reduces the amount of risk associated with that portfolio.
A Non-Random Walk Down Wall Street
There is another school of thought that considers the markets efficient yet predictable. One of the
leading proponents is Andrew Lo. Lo earned his Ph.D in economics at the University of Chicago and
is currently a Professor of Finance at the Sloan School of Management at MIT. Lo is a bit of an odd
ball among academics because of his beliefs regarding the efficient market hypothesis and his
attraction to technical analysis. Lo and Mackinlay's book A Non-Random Walk Down Wall Street debunks
many of the theories put forth in the 1973 classic with a similar name. (Remember that most
academics subscribe to the random walk theory.) Lo's research concluded the following:
It is not only plausible that markets are efficient, but participants can also profit from efficient
markets. However, Lo asserts that even though it is possible to outperform the markets, it requires
ongoing research, continuous improvement and constant innovation. Beating the market does not come
easy, nor is it something that is easy to maintain. Lo likens the pursuit of above-average returns
to that of a company trying to maintain its competitive advantage. After introducing a hot new
product, a company cannot just sit back and wait for the money to roll in. In order to remain above
the competition, management must be flexible and look for ways to continuously improve and innovate.
Otherwise the competition will overtake them. Money managers, traders and investors who find ways to
outperform the market must also remain flexible and innovative. Just because a method works today,
does not mean it will work tomorrow. In an interview with Technical Analysis of Stocks and
Commodities, Lo sums it up by stating:
"The more creativity you bring to the investment process, the more rewarding it will be.
The only way to maintain ongoing success, however, is to constantly innovate. That's much the same
in all endeavors. The only way to continue making money, to continue growing and keeping your profit
margins healthy, is to constantly come up with new ideas."
Conclusions
These rebuttals to random walk theory are not meant to suggest that the vast majority of individuals
are going to suddenly start outperforming the market. Even though this may be true over the past
3 years, history suggests that it is not likely to be the case 10 years from now. In other words,
history suggests that this is an anomaly and there will be a reversion to the mean. Nonetheless, the
investment and trading landscape has changed drastically over the last 20 years, even over the last
5 years. Individuals have access to more information and tools, transactions costs are negligible,
trades are executed almost instantaneously, equity mutual funds have improved their performance and
the buy-and-hold strategy does not appear to be a profit maximizing strategy. It should come as no
surprise that analysis can make a difference. The only question is which type: fundamental analysis,
technical analysis or both?