Parameter risk
risk of assuming incorrect distributions or parameters for those distributions
Components of parameter risk (3)
Estimation risk
uncertainty arising from having only a sample of possible data to estimate parameters
Largest source of parameter risk
projection risk
Coefficient of variation of total claims and what it measures
CV ( S ) = [ ( Var ( N ) / E [ N ] + CV ( X )^2 ) / E [ N ] ] ^ .5
*measure of projection risk
larger CV = more risk
Relationship b/w size and risk for CV
more risk for smaller companies
however, as projection risk increases, rises more for large companies because small companies are already volatile
Components of projection uncertainty (2)
2. uncertainty in fitted trend line
Relationship b/w claim severity trend and general inflation
claim severity trend > general inflation
> > excess is called social inflation or superimposed inflation
Relationship b/w uncertainty and time when analyzing trend
prediction intervals widen over time (b/c of uncertainty in the trend rate)
Method to assess estimation risk
use the covariance matrix from MLE procedure and assume the parameters come from a joint lognormal distribution
What is a copula?
combination of individual marginal distributions into a multivariate distribution to force correlation in specific areas
F ( x, y ) = Pr ( X < x and Y < y ) = C ( u, v )
or = C ( F ( x ), F ( y ) )
where u, v are percentiles of X and Y
Simulation process using copulas (3 steps)
Which copulas (3) are invertable and why does this matter?
** if copulas are invertable, they can be simulated
Common copula ranks in terms of right tail correlation (least to most)
Frank < Normal < Gumbel < HRT
Purpose of tail concentration functions / L-R graph
provides a quantification of tail strength
> > L ( z ) and R ( z ) are measures of correlation
L-R graph
L ( z ) and R ( z ) against z which exists on [0,1]
Left tail function - L ( z ) and lower tail dependence parameter
L ( z ) = C ( z, z ) / z
lower tail dependence parameter = limit of L ( z ) as z»_space; 0
Right tail function - R ( z ) and upper tail dependence parameter
R ( z ) = ( 1 - 2 * z + C ( z, z ) ) / ( 1 - z )
upper tail dependence parameter = limit of R ( z ) as z»_space; 1
Methods to model projection risk (2)
Simple trend model understates projection risk especially for long tailed lines
Methods to compare tail behavior between 2 copulas (2)
2. Plot joint density functions and compare density in the tails
Components of an internal risk model (IRM - 4)
Recommendations for IRM startup (4)
Recommendations for parameter development in an IRM (4)
Recommendations for implementation of an IRM (4)