The
mathematics of
Mathematics confirms what we knew all along theres no such
thing as easy money
by Dr. Florin Diacu
o
you hope to win the lottery some day? If not, youre a happy exception.
Why happy? Because if you buy a ticket your chances of winning are extremely
small. A computation any math sophomore can do shows that the probability
of getting all the numbers right at a 6/49 draw is approximately 1 in
14 million. Its even worse for the 7/49: 1 in 86 million.
No one can beat the mathematics. The last
few 6/49 results tell that it takes about 140 million tickets, sold
over several draws, to make 9 or 10 perfect winners. The statistics
agree with the laws of probability.
Your chances of getting killed in a car
accident this year are bigger than one in 100,000, which means that
you could die a thousand times before winning the lottery. Still, most
people gamble and only a few fear driving.
What about the stock market? Are our chances
better there? The common wisdom says they are. Were told to consult
an expert, get a well-balanced portfolio, dont panic, ignore the
fluctuations, invest long term and our future is secure. Or is it? Lets
see what history tells us.
Between the late 1870s and early 1920s
the graph of the average stock price (rescaled to inflation) looks like
the profile of a mountain range with a deep valley at the beginning
and another at the end, both at about the same height. In other words,
money invested in a hypothetical index fund in 1878 won nothing if retrieved
in 1921. Then things improved all of a sudden.
In 1929 stock prices reached an unprecedented
high, twice above any previous peak and about 10 times the minimum of
the 1920s. Returns were low, but nobody cared. The press of the time
shows that investors were exuberant: the market goes only up, nothing
can stop its hike; even if something bad happens, those in charge will
fix the problem; we are safe.
Diacu (with
someone elses lottery tickets)
(Valerie Shore photo)
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But stock prices went down, then up and
down; every dip reached below the previous. In 1933 the market fell
to an absolute low, lower than 12 years before. The depression loomed
large and the level of unemployment made life very difficult. World
War II began and led to a global disaster. As a consequence, the economy
needed several decades to recover.
In the late 50s stock prices finally
hiked to the level of 1929. Then they went down and up again. They have
been above the 1929 peak only since the mid-80s. All these historical
facts are in sharp contrast with the myth of secure long-term stock-market
investments.
From 1994 to the early 2000 the Dow Jones
Industrial Average, which measures the health of the American economy,
sky rocketed from 3,600 to 11,700 points. Corporate profits, however,
rose less than 60 per cent, and that from a depressed base. During the
same period, living standards increased very little. Similar things
had happened between 1922 and 1929.
Since its peak in the year 2000, like
in the early 1930s, the market went down. The events of last Sept. 11
seem to have accelerated this trend. Does this decreasing average of
most indexes resemble what happened between 1930 and 1933? Are we on
the brink of a depression? Not necessarily. In fact, nobody knows. But
it doesnt take an expert to understand that if the market continues
to drop, people will lose confidence, sell, and make stock prices plunge
even more. In the end, the attitude of investors is what drives the
market up or down. It took more than 30 years to rebuild the trust lost
after the plunge of the 1930s.
Whereas the mathematics of lotteries is
simple, the mathematics of the stock market is very complicated. Some
of the mathematical results obtained in this direction were awarded
the Nobel Prize for economics. They help us understand many aspects
of the economy but they dont get too far.
Though attempts are being made to forecast
the market, theyre of no practical use yet. Stock prices show
all the characteristics of chaotic dynamic systems, which form an active
research area in mathematics. The behaviour of those systems is as unpredictable
as the weather.
If playing the lottery will make us neither
rich nor poor, investing pensions or education funds in stocks is a
risk based on irrational assumptions. The only reason for such actions
lies in a myth unjustified by history and unsupported by any reliable
mathematical model.
Though we know little about the moods
of the market, one thing is for sure: a sharp drop in stock prices will
affect us all whether we invested in stocks or not. But depending on
many factors, including the adopted financial strategy, some will be
more touched than others. So lets hope for the best and be prepared
for the worst an attitude that could save us a lot of grief in
the future.
Dr. Florin Diacu is a UVic mathematics professor and the UVic site
director of the Pacific Institute for the Mathematical Sciences.