Final Review Flashcards
Benktander
Formula and Pro/Cons
% reported * C-L Ult + % unreported * B-F Ult
Cum Losses + % unreported * B-F Ult
Advantages:
* Almost always has a smaller MSE than C-L and B-F Method
* Incorporates prior expectation of losses rather than fulyl relying on paid/reported losses to date (like the C-L)
Hurlimann
Ult, Credibility, ELR, p
Ult = Z * C-L Ult + (1-Z) B-F Ult
Credibility Z
* Z(GB) = p = % reported
* Z(WN) = p * ELR
* Z(OC) = p / [ p+sqrt(p) ] = p / ( p + t )
ELR
* m = incremental LR = sum(loss) / sum(premium)
* ELR = sum(m’s)
p = sum(m’s) / ELR for each AY
C-L = Individual | B-F = collective
Hurlimann
What Happens When Var(U) > Var(U_bc)?
- f increases
- t increases
- Z decreases
- more weight to B-F (collective) method
Brosius
What Happens When Intercept or Slope < 0?
Set intercept = 0 (C-L method)
Set slope = 0 (ELR method)
Brosius
Caseload Effect, Credibility Weighted Ultimate
All steps, another way to say VHM/EPV
% reported at 12 months = dy + x0
Z = VHM / (VHM + EPV)
VHM = Variation due to Loss Occurrence Process
EPV = Variation due to Loss Reporting Process
L(X) ult = Z * (x - x0)/d + (1-Z) * ELR Ult
USE ORIGINAL SCENARIO FOR ELR ULT
Brosius
Hugh White’s Question
3 Scenarios
Cov(X,Y) = Var(X) –> IBNR unchanged (B-F Method)
Cov(X,Y) < Var(X) –> decrease IBNR (ELR Method)
Cov(X,Y) > Var(X) –> increase IBNR (C-L Method)
Clark
Cape Cod Setup
Weibull
X = 6, 18, 30, etc
% Paid = G(X) = 1- exp( -(x/θ)^w )
Used-Up Prem = G(X) * OLEP
% Unpaid = 1 - G(X)
ELR = sum(Cum Loss) / sum(Used-Up Prem)
Ult = Cum Loss + % unreported * ELR * OLEP
Clark
Log-Likelihood
All steps/formulas
Expected Incremental Triangle = Incremental G(X) * ELR Ult
MLE Triangle = Actual * ln(Expected) - Expected
Log-Likelihood = sum(MLE Triangle)
Mack
Reserve Confidence Interval
All Formulas
Var = ln(1+ SE(reserves)^2 / reserves^2)
Confidence Interval = Reserves * exp(-Var/2 ± Z * SD)
Venter
Parameterized BF Method: h(w) / f(w)
What is it? + both formula
Variance is assumed to be constant
h(w) ~ kind of like ultimate loss, but ONLY to be used with f(d) to get expected reserves
f(d) ~ incremental % reported
If variance assumed to be constant:
* h(w) = sumprod[ f(d), incremental loss ROWS] / sumSQ[ f(d) ]
* f(d) = sumprod[ h(w), incremental loss COLUMNS] / sumSQ[ h(w) ]
w for the years, d for development period
Venter
Starting f(d) - seed
If not given in the problem:
* Incremental % Reported (first get % reported = 1/CDF)
* = incremental LDF / CDF
Venter
SSE and Adjusted SSE
SSE Triangle = (Actual - Expected)^2
SSE = sum(SSE Triangle EXCLUDING 1ST COLUMN)
Adjusted SSE = SSE / (n-p)^2
where n = # of values in triangle excluding the first column
p = number of parameters
C-L and CC: p = d - 1
BF: p = 2d - 2
where d = # of development periods
Venter
AIC / BIC
AIC = SSE * exp(2p/n)
BIC = SSE * n^(p/n)
where n = # of values in triangle excluding the first column
p = number of parameters
C-L and CC: p = d - 1
BF: p = 2d - 2
where d = # of development periods
Venter
Alternative Emergence Patterns
Linear with constant = f(d) * c(w,d) + g(d)
* Highly variable and slowly reporting lines (XS reinsurance)
Factor * Parameter = f(d) * h(w)
* Parameterized BF model
* Cape Cod has h(w) = h (constant)
Shapland
Unscaled Pearson Residual
= (actual - expected) / sqrt(expected^z)
USING INCREMENTAL LOSSES
The power, z, is used to specify the error distribution
* z = 0 for normal
* z = 1 for poisson
* z = 2 for gamma
* z = 3 for inverse gaussian