common risk measures descriptions and comparisons william c. wojciechowski vigre computational...
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Common Risk MeasuresDescriptions and Comparisons
William C. Wojciechowski
VIGRE Computational Finance Seminar
Rice University
October 15, 2003
Defining Risk
What is risk? How is risk measured? Types of risk – market, credit, liquidity, etc. Finance is one area of risk management
Against The Gods: The Remarkable Story of Risk - Peter L. Bernstein
Defining Risk
Risk - chance that an investment’s return will be less than expected.
Market Risk – loss in value due to decline in price
Event Risk – catastrophic actions cause decrease in value
Liquidity Risk – lose value by not being able to transact
Measuring Risk
X - a random variable representing the value of an investment at some future time t
Scalar, such as volatility of X?
Vector, such as a value and probability?
Consider the whole distribution of X?
Common Risk Measures
Dispersion Measures
Common Risk Measures
More dispersion does NOT equal more risk
Normal mixture model with possible large win
Normal model without possible large win
Common Risk Measures
More dispersion does NOT equal more risk
Cu
mu
lativ
e R
etu
rn
0 50 100 150 200 250
05
01
00
15
02
00
25
0
Cumulative Return Comparison
SD(Black) = 3.19 SD(Orange) = 0.96
Common Risk Measures
More dispersion does not equal larger positive returns
Cu
mu
lativ
e R
etu
rn
0 50 100 150 200 250
-20
0-1
50
-10
0-5
00
Cumulative Return Comparison
SD(Black) = 2.96 SD(Orange) = 1.02
Common Risk Measures
Dispersion below a target Fishburn family
Common Risk Measures
VAR (Value at Risk) Measures
Common Risk Measures
Accumulate VAR (AVAR)
Common Risk Measures
Simulations– Generate random return streams X and Y– For each risk measure, calculate the risk of X and Y– Count the number of times the risk measure makes
the correct decision
Simulations
Possibility of large gain
Simulations
Moderate chance of large loss
Simulations
Small chance of catastrophic loss
Conclusions
There are many possible measures of risk
Appears none of the common risk measures universally applies to all situations
Research opportunities are abundant
Reference
Guy Kaplanski and Yoram Kroll, “VAR risk measures vs traditional risk measures: an analysis and survey”, Journal of Risk, 4, Spring, 2002