Kreps Flashcards
Total assets and what is supported by each component (2)
Kreps
total assets = reserves + surplus
reserves support mean of assets & liabilities
surplus supports variability of assets & liabilities
Total capital (C)
Kreps
total capital = mean outcome + risk load
Desirable qualities for an allocatable risk load (3)
Kreps
- ability to be allocated to any level
- allocated risk load for a sum of random variables should = sum of individually allocated risk load amounts
- same additive formula is used to calculate risk loads for any sub-group or grouping
General form of riskiness leverage models
Kreps
R = integral of f(x) * (x - mu) * L(x) dx
f(x)dx can be called dF-bar for joint probability distributions
where f(x) = joint probability distribution and L(x) = riskiness leverage function for total losses
Risk load (R) and capital (C) across multiple LOB
Kreps
R = sum of R(k)'s C = sum of C(k)'s
where k = individual LOB
Advantage of co-measures
Kreps
they are automatically additive
Disadvantage of co-measures
Kreps
can be challenging to find appropriate forms of the riskiness leverage function L(x)
Conditions for negative risk loads (2) and when it is desirable
(Kreps)
- x(k) < mean
- large L(x)
desirable for hedges, occurs when there is a low correlation with total losses
Properties of riskiness leverage models (4)
Kreps
- desirable qualities for allocatable risk loads are satisfied
- no risk load for constant variables - R(c) = 0
- risk load will scale with change in currency - R(lambda * x) = lambda * R(x)
- may not produce a coherent risk measure
Coherent risk measures
Kreps
satisfy sub-additivity requirement
R(x + y) <= R(x) + R(y)
Super-additivity
Kreps
R(x + y) > R(x) + R(y)
not coherent
Types of riskiness leverage functions, L(x) (7)
Kreps
- risk-neutral
- variance
- VaR
- TVaR
- semi-variance, SVaR
- mean downside deviation
- proportional excess
Risk-neutral form of the riskiness leverage function, L(x)
Kreps
L(x) = c
Situations when a risk-neutral form of L(x) might be appropriate (2)
(Kreps)
- risk of ruin if risk of ruin is very small compared to capital OR capital is infinite
- risk of not meeting plan if indifferent about making plan
Variance form of the riskiness leverage function, L(x)
Kreps
L(x) = (beta / surplus) * (x - mu)
Relevant part of the distribution when using the variance form of L(x)
(Kreps)
entire distribution (just as much risk associated with good & bad outcomes)
Surplus (S) when using the variance form of L(x)
Kreps
S = sqrt(beta * var(x))
Forms of the riskiness leverage function, L(x) where the risk load increases quadratically (2)
(Kreps)
- variance
2. semi-variance, SVaR
TVaR form of the riskiness leverage function, L(x)
Kreps
L(x) = theta(x - x(q)) / (1 - q)
where theta is a step function with:
theta(x) = 0 for x <= 0 and
theta(x) = 1 for x > 0
x(q) = value of x so F(x(q)) = q