Evidence suggests that the
credit-market turmoil of recent months owes as much to bad math,
dubious academic theories, false assumptions, and inadequate risk
models as it does to speculative excess and an unhealthy reliance
on borrowed money.
In fact, some would argue that
widespread ignorance about the true nature of the first four
played a strong role in fostering the latter two. In sum, they
gave the erroneous impression that risky decisions were being made
with scientific precision and inspired a false sense of confidence
among managers, regulators, and investors.
In a Financial Times
commentary, "The
Pseudo-Science Hurting Markets," Nassim Nicholas Taleb,
author of The Black Swan: The Impact of the Highly Improbable,
details the precarious foundations upon which billions -- perhaps
trillions -- of dollars have been invested.
Last August, The Wall Street
Journal published a statement by one Matthew Rothman,
financial economist, expressing his surprise that financial
markets experienced a string of events that “would happen once
in 10,000 years”. A portrait of Mr Rothman accompanying the
article reveals that he is considerably younger than 10,000
years; it is therefore fair to assume he is not drawing his
inference from his own empirical experience but from some
theoretical model that produces the risk of rare events, or what
he perceives to be rare events.
The theories Mr Rothman was using
to produce his odds of these events were “Nobel-crowned”
methods of the so-called modern portfolio theory designed to
compute the risks of financial portfolios. MPT is the foundation
of works in economics and finance that several times received
the Sveriges Riksbank Prize in Economic Sciences in Memory of
Alfred Nobel. The prize was created (and funded) by the Swedish
central bank and has been progressively confused with the
regular Nobel set up by Alfred Nobel; it is now mislabelled the
“Nobel Prize for economics”.
MPT produces measures such as “sigmas”,
“betas”, “Sharpe ratios”, “correlation”, “value at
risk”, “optimal portfolios” and “capital asset pricing
model” that are incompatible with the possibility of those
consequential rare events I call “black swans” (owing to
their rarity, as most swans are white). So my problem is that
the prize is not just an insult to science; it has been putting
the financial system at risk of blow-ups.
I was a trader and risk manager
for almost 20 years (before experiencing battle fatigue). There
is no way my and my colleagues’ accumulated knowledge of
market risks can be passed on to the next generation. Business
schools block the transmission of our practical know-how and
empirical tricks and the knowledge dies with us. We learn from
crisis to crisis that MPT has the empirical and scientific
validity of astrology (without the aesthetics), yet the lessons
are ignored in what is taught to 150,000 business school
students worldwide.
Academic economists are no more
self-serving than other professions. You should blame those in
the real world who give them the means to be taken seriously:
those awarding that “Nobel” prize.
In 1990 William Sharpe and Harry
Markowitz won the prize three years after the stock market crash
of 1987, an event that, if anything, completely demolished the
laureates’ ideas on portfolio construction. Further, the crash
of 1987 was no exception: the great mathematical scientist Benoît
Mandelbrot showed in the 1960s that these wild variations play a
cumulative role in markets – they are “unexpected” only by
the fools of economic theories.
Then, in 1997, the Royal Swedish
Academy of Sciences awarded the prize to Robert Merton and Myron
Scholes for their option pricing formula. I (and many traders)
find the prize offensive: many, such as the mathematician and
trader Ed Thorp, used a more realistic approach to the formula
years before. What Mr Merton and Mr Scholes did was to make it
compatible with financial economic theory, by “re-deriving”
it assuming “dynamic hedging”, a method of continuous
adjustment of portfolios by buying and selling securities in
response to price variations.
Dynamic hedging assumes no jumps
– it fails miserably in all markets and did so
catastrophically in 1987 (failures textbooks do not like to
mention).
Later, Robert Engle received the
prize for “Arch”, a complicated method of prediction of
volatility that does not predict better than simple rules – it
was “successful” academically, even though it underperformed
simple volatility forecasts that my colleagues and I used to
make a living.
The environment in financial economics
is reminiscent of medieval medicine, which refused to
incorporate the observations and experiences of the plebeian
barbers and surgeons. Medicine used to kill more patients than
it saved – just as financial economics endangers the system by
creating, not reducing, risk. But how did financial economics
take on the appearance of a science? Not by experiments (perhaps
the only true scientist who got the prize was Daniel Kahneman,
who happens to be a psychologist, not an economist). It did so
by drowning us in mathematics with abstract “theorems”. Prof
Merton’s book Continuous Time Finance contains 339 mentions of
the word “theorem” (or equivalent). An average physics book
of the same length has 25 such mentions. Yet while economic
models, it has been shown, work hardly better than random
guesses or the intuition of cab drivers, physics can predict a
wide range of phenomena with a tenth decimal precision.
Every time I have questioned
these methods I have been abruptly countered with: “they have
the Nobel”, which I have found impossible to argue with. There
are even practitioner associations such as the International
Association of Financial Engineers partaking of the cover-up and
promoting this pseudo-science among financial institutions.
The knowledge and risk awareness we are accumulating from the
current subprime crisis and its aftermath will most certainly
not make it to business schools. The previous dozen crises and
experiences did not do so. It will be dying with us, unless we
discredit that absurd Sveriges Riksbank Prize in Economic
Sciences in Memory of Alfred Nobel commonly called the “Nobel
Prize”.