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It was with some irony that the first Canadian Investment Review
Risk Management Conference was held on the one-year anniversary
of one of the most significant market crises of the century. On
Aug 27, 1998, one year prior to the date of the conference, the
TSE35 fell 7.4% and began a three-day sell off that totaled 11.5%.
During that same three-day period the S&P500 lost 12.1% of its
value and CBOE Volatility Index, a proxy for the market perception
of implied option volatility, moved from 31% to 48%.
Despite unprecedented investment in sophisticated risk management
systems, many hedge funds, investment dealers and commercial banks
experienced extraordinary losses during that period. For example,
Long Term Capital Management (LTCM) lost 44% of their capital in
the month of August. Other financial institutions experienced similar
losses. Table 1 presents the change in revenue from 2nd to 3rd quarter
of 1998 for Long Term Capital Management, Salomon Smith Barney,
J.P. Morgan and Merrill Lynch.
Table 1 illustrates the enormous magnitude of the losses experienced
in the 3rd quarter of 1998. More shocking, however, is the size
of the losses in comparison to the quantity of market risk on the
books of these firms as indicated by their Value at Risk, or VaR
statistics.
VaR is a widely applied measure of market risk. The VaR of a portfolio
is the level of loss in market value that should not on average
be exceeded with a given probability (typically 99%). In other words,
the VaR is the dollar value loss that should not be exceeded 99%
of the time.
LTCM put enormous reliance on VaR, as did other market participants.
In fact, the Bank for International Settlements (BIS) requires that
a version of VaR be used by all commercial banks to establish the
amount of capital required to support their market risk taking operations.
As a result of this requirement many commercial banks have made
VaR the central component of their risk management system. In addition
to commercial banks, investment dealers actively use VaR to measure,
monitor and limit market risk taking.
LTCM and Merrill Lynch experienced losses approximately 40 times
the size of their VaR, Salomon Smith Barney about 30 times their
VaR and J.P. Morgan 25 times their VaR statistic. Table 1 reports
the probability of incurring losses of this magnitude under the
assumption that market returns follow a normal distribution.
The loss incurred by LTCM is statistically equivalent to consecutively
flipping 768 heads in a fair coin toss, a feat that would take 4
hours and 16 minutes at a speed of 1 flip per 20 seconds. This can
be contrasted to the experiment held during the conference in which
approximately 40 participants each tossed a fair coin and recorded
the number of consecutive heads. Of the of 40 participants, nobody
tossed more than five consecutive heads, an outcome with a probability
of approximately 3%, a total 150 times less than the 768 consecutive
tosses implied by the LTCM 3rd quarter results.
In fact, these losses were less likely to occur, given their estimated
VaR, than the probability of a chimpanzee sitting at a computer
keyboard and randomly entering the following sequence of 64 key
strokes: "there are three types of lies: lies, damn lies, and
statistics"- an outcome that has a probability or likelihood
of less than 1 in 1026.
There are four conclusions to be drawn from the trading results
of these and other firms in 1998:
* The amount of market and credit risk on the balance sheet of
these firms during the 3rd quarter of 1998 was significant.
* VaR did not provide an accurate measure of this market risk
and of the potential losses for these firms.
* The investment made by these firms in risk management technology
failed to prevent or control losses.
* The investment in risk management technology encouraged risk
taking that was not properly measured or monitored and ultimately
led to significant losses.Ironically, the root of the problem for
these firms may have been the very VaR model that was designed to
assist firms in avoiding the enormous losses they experienced in
1998. The problem is simple. The assumptions inherent in most VaR
models are invalid in times of market crisis. More specifically:
* The assumption that returns follow a normal distribution does
not properly reflect the probability of massive market moves, and
* The correlation among financial instruments that results in
times of crisis in no way resemble the correlation among the same
financial instruments that results in times of market calm.This,
combined with the fact that the structural integrity of a portfolio
is most tested in time of a crisis, implies that an overreliance
on a VaR model as a risk management tool may lead to serious mis-specification
of the risk inherent in a portfolio of risky assets. In fact, the
firms listed in Table 1 had considerably more "Value at Risk"
than indicated by their VaR model. The systematic under-estimation
of VaR led to a substantial increase in the level of risk taking
and ultimately to significant trading losses among hedge funds,
investment dealers and commercial banks.
Risk Attribution
Methodologies such as VaR have distracted risk managers from developing
suitable approaches to the management of risk. Risk management is
a large-scale data problem. There are numerous risks that can potentially
affect the performance of a portfolio. In order to reduce "risk"
to a measurable quantity, we typically compute generalized statistics.
VaR is such a statistic. However, it is important to keep in perspective
what VaR is and VaR is not.
VaR is- an important statistic useful for summarizing certain properties
of a portfolio, an important part of a comprehensive risk management
system.
VaR is not- the only statistic required to summarize the properties
of a portfolio, a substitute for a comprehensive risk management
system.
Just as the medical profession does not rely solely on a single
diagnostic such as body temperature to determine the health of human
being, risk managers should not rely solely on VaR to determine
the health of a portfolio of risky assets. Instead, risk managers
should apply a variety of methods. Comprehensive risk management
systems combine the use of statistical risk measures such as VaR
with other techniques such as stress testing, scenario analysis
and visualization.
There are two essential steps to determining the risk condition
of a portfolio:
* The identification of the risk attributes and valuation attributes
of the portfolio, and
* The quantification of the effect these risk attributes will
have on the valuation attributes of the portfolio through summary
statistics, scenario analysis and stress testing.Risk attribution
is the process of identifying and quantifying the risk inherent
in a transaction, portfolio or collection of portfolios. Generally
the attributes of a transaction, portfolio or collection of portfolios
are either risk attributes or valuation attributes.
Risk attributes are the variables that effect the valuation attributes
of a transaction, portfolio or collection of portfolios. Interest
rates, time to maturity, foreign exchange rates, implied volatility
and inflation are examples of risk attributes.
Valuation attributes are the summary statistics that describe the
valuation properties of a transaction, portfolio or collection of
portfolios. Present value, expected value, VaR, cashflow, duration,
convexity, carry and vega are examples of valuation attributes.
Once the risk attributes and valuation attributes are identified,
scenario analysis and stress testing techniques are used to vary
the risk attributes and study their effect on the valuation attributes.
Risk attribution is similar to portfolio performance attribution
with a simple distinction: performance attribution assigns past
performance to risk attributes, whereas risk attribution assigns
future risk to risk attributes. Risk attribution tests the effect
risk attributes will have on future portfolio performance. The output
of the stress test or scenario analysis is a large amount of data
that must be evaluated. The most efficient approach to evaluating
the data is through visualization. Using multi-dimensional visualization
techniques risk managers can quickly assess the effect that certain
risk attributes will have on the performance of their portfolio.
Risk attribution provides simple framework for analyzing the risk
of a transaction or portfolio. To illustrate consider the following
simple example.
Assume we have a fund with a simple 20-year liability. For years
1 through 10 the annual cashflow of our simple liability is $0.
However, for years 11 through 20 the annual cashflow of our liability
will be $5mm, indexed to the rate of inflation from the starting
date of the liability to the cashflow date. To hedge this liability
we form a portfolio of three hedge instruments: 1) a 10 year risk
free par bond, 2) a 20 year risk free par bond and 3) a Real Return
Bond paying a 4% coupon and maturing in 2021. The objective of the
analysis is to determine whether a real return bond is a more effective
hedge for an inflation indexed liability than a simple coupon bond.
There are two risk attributes that are important to analyze for
this simple hedging problem: interest rates and inflation. Table
2 summarizes the sensitivities of the liabilities and hedge instruments
to changes in the two risk attributes.
Obviously, the price of the coupon bonds is sensitive only to changes
in interest rates and is not affected by changes in inflation. The
liability and the RRB are affected by both interest rates and inflation.
Notice that when both inflation and interest rates move together,
the value of both the liability and the RRB are invariant to the
changes.
Figure 1 provides visually the output of a scenario analysis of
the residual risk for our liability hedged with only the 10-year
and 20-year bonds. Interest rates and inflation rates were varied
independently and the liability and hedge instruments revalued for
each scenario. Notice that for changes in interest rates the hedge
performs well, but for changes in the inflation rate the bonds provide
no hedge at all.
Figure 2 provides visually the output of a scenario analysis of
the residual risk for our liability hedged with the 10-year and
20-year bonds and the RRB. Again, interest rates and inflation rates
were varied independently and the liability and hedge instruments
revalued for each scenario. The hedge performs well for changes
in both inflation and interest rates. Figure 3 overlays the bond
only hedge and RRB hedge for comparison. For scenarios in which
inflation and interest rates move in tandem (are positively correlated)
the RRB hedge significantly outperforms the bond only hedge. Using
very simple risk management techniques we have determined the usefulness
of hedging inflation linked liabilities with real return bonds.
Conclusion
Methodologies such as VaR are but a small component of a comprehensive
risk management process. The intense focus on VaR as a risk management
tool has in many cases led to a mis-specification of market risk
among hedge funds, investment dealers, commercial banks and other
managers of financial risk. The result in many cases has been an
unmonitored increase in risk taking, which played a significant
role in the performance of many market participants in the 3rd quarter
of 1998. As well, the obsession with VaR has distracted risk managers
from developing more suitable approaches. Risk management is a large-scale
data problem. Statistics such as VaR help reduce "risk"
to a measurable quantity. But due to the limitations of the assumptions
that underlie most VaR methodologies, risk managers should not rely
solely on VaR. Instead, risk managers should apply a variety of
methods to help determine the risks inherent in their portfolios.
Comprehensive risk management systems combine the use of statistical
risk measures such as VaR with other techniques such as stress testing,
scenario analysis and visualization. Risk attribution provides a
simple framework for applying these tools to risk management. Such
an approach relies less on simplifying assumptions and provides
a visual road map that helps describe the nature of the risk of
our portfolios.
Michael Durland is deputy head of the capital markets group,
Scotia Capital.
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