ica modelling seminar parameter uncertainty peter tavner, gavin hill, trevor maynard
DESCRIPTION
IntroductionTRANSCRIPT
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ICA Modelling SeminarParameter UncertaintyPeter Tavner, Gavin Hill, Trevor Maynard
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Agenda
Introduction Catastrophe Modelling Specific areas of uncertainty
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Introduction
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Uncertainty: the problem
We have been asked to calculate remote scenarios We have:
limited data some theory some tools our actuarial judgement ..and lots of ‘expert opinion’
In the context of a 99.5% CI, we can never say with certainty that the ICA number is ‘correct’
…but how far out are we?
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The response so far?
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The response so far?
Many ICAs do not fully acknowledge the issue of uncertainty. Why not? Insufficient awareness of tools and methods Insufficient data in first place => guesstimates Difficult to sell internally Other priorities Likely to increase the number!
Are actuaries in danger of over-promising?
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Drivers of Uncertainty
Parameter Uncertainty Specific to our data sample Beyond the data
Model error Convergence error, process error
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Parameter uncertainty Parameter estimate is based on population
sample It will always be an estimate, hence uncertain Different estimation methods will give different
answers e.g. Maximum likelihood Method of moments
But you do need some data in first place!
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Identifying Parameter Uncertainty
Keeping it simple: back test the results Conventional statistical methods
Confidence intervals Goodness of fit tests Asymptotic distribution of ML estimator
Bayesian approach
Note: explicitly incorporating parameter uncertainty can materially impact distributions
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Parameter Uncertainty (2)
Beyond the data: is the past a reliable guide to the future? Regulatory/legal changes e.g. Ogden Latent claims
Very difficult to capture explicitly Sensitivity test the results
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Other sources
Model Error The best fit may not be the true underlying Over-parameterisation can be an issue
Convergence 10,000 sims may be insufficient Problem worse with risk measures that look further into tail Technical solutions available: stratified/importance sampling
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What the guidance says
FSA sector briefing (Nov 2005):“important that firms recognise the issue”“that uncertainty is adequately communicated”“not appropriate to ignore this risk”
Lloyd’s:“Adopt prudent assumptions to compensate for known
shortcomings including parameter uncertainty”
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The bigger picture
ICAS is not just about the number, it is also the framework Remember the ICA process is intended as a tool to
inform management Use statistical methods (and judgement) to identify
risk areas and weaknesses Communication important : better to flag areas of
uncertainty than do nothing Keep the ICA strictly ‘best estimate’? Discuss
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Catastrophe modelling
Parameter Uncertainty
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Types of uncertainty
Aleatory inherent randomness cannot be reduced by collation of additional data
Epistemic lack of information/understanding can be reduced
Useful concepts
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Epistemic sources Hazard data is scarce!
a few hundred years at most of very low probability events
Limited scientific knowledge
Cross disciplinary nature Actuaries Structural Engineers Climate Scientists/ Seismologists
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(more) epistemic sources Exposure data
often poor – lack of GIS data but important
E.g soil type can vary within small area but crucial for earthquake damage
Insured values often uncertain
Damage functions Based on laboratory models Models within models!
GIS = Geographic Information Systems = geographically referenced data
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Knowledge wave; modelling wave (lag) – Find out what’s known Ask your modelling company their view
Modelling Co’s are “silent” on this
Some of the parameter uncertainty is built in secondary uncertainty damageability factors
Understand the choices they have made on your behalf E.g. RMS near term view/ AIR long baseline
General Comments
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Event ID SSI Central Pressure (mb)
Radius of Max Winds (mi.)
Forward Speed (mph) Landfall Latitude Landfall
Longitude Landfall Location
1 5 913.5 8 15 30.3 -81.4 Jacksonville
2 4 930.7 10 15 30.3 -81.4 Jacksonville
3 3 956.4 12 15 30.3 -81.4 Jacksonville
4 2 973.5 15 15 30.3 -81.4 Jacksonville
….
30 1 982.1 15 15 30.1 -85.8 Panama City
FCHLPM scenarios
Florida Commission on Hurricane Loss Projection Methodology
For certification 4 model companies complete returns Public results
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FCHLPM scenarios - results
Florida Commission on Hurricane Loss Projection Methodology
AIR ARA Eqecat RMS 5,387,021 13,579,563 14,619,000 11,244,471
3,369,452 8,774,355 8,397,000 5,964,194
736,047 1,742,091 2,433,000 1,652,508
208,825 379,178 629,000 498,050
…….
32,330 57,075 209,000 115,176
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FCHLPM scenarios - results Average range62% to 150% of mean Is your ICA result that uncertain? Different models give very different results The science is not exact!!!
0 5 10 15 20 25 30
0 e
+00
1 e
+07
2 e
+07
3 e
+07
4 e
+07
5 e
+07
EventID
Loss
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Source: Grossi and Kunreuther. Catastrophe Modelling, Springer 0-387-23082-3
Parameter risk can be huge.
Ground up losses 3 models + Wharton School 99.5%ile
$0bn, or $3bn!!
Why? No data
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“ A little knowledge is a dangerous thing; drink deep, or taste not the Pierian Spring: there shallow draughts intoxicate the brain, and drinking deeply sobers us again”
Alexander Pope – an essay on Criticism 1709
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Catastrophe modelling
Climate change
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“Climate change poses risks to a large number of general insurers….it became apparent that some firms may rely too much on the outputof their catastrophe models without proper consideration of the inputs….it is imperative that firms address this issueUrgently” FSA Financial Risk Outlook 2006
http://www.fsa.gov.uk/pubs/plan/financial_risk_outlook_2006.pdf
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“….it is not acceptable to wait until the effects of the trend are wellunderstood before commenting on the possible implications… consider scientific evidence on climatechange with regards to parameter setting”
http://www.lloyds.com/
Lloyds ICA guidance 2006
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Why wait?
There is no justifiable reason any more:
Climate change is happening Even the (sane) sceptics agree There is sufficient information to do something
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The AMO
or is it?…….
Source: Atlantic Ocean Forcing of North American and European Summer ClimateRowan T. Sutton* and Daniel L. R. Hodson
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The AMO
-0.4
-0.2
0.0
0.2
0.4
1871
1875
1880
1885
1890
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
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Means cycle 2.46 high mode 3.18 low mode 1.91
Num
ber o
f maj
or h
urric
anes
AM
O in
dex
01
23
45
67
-0.4
-0.2
0.0
0.2
0.4
1871
1875
1880
1885
1890
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
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Simple model
Hurricane formation rate 3.18/2.46-1 = 29% above average (could say 4/2.46) Assume constant landfall proportion (25%)
From NHC data debatable probably higher in hot phase
Assume poisson landfall process, Xt
Assume capital proportionate to 99.5%ile of Xt
=> Required Capital increases by 20%
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Intense Hurricane Risk
“we don’t know the right answer….”
Correct But zero is definitely the wrong answer Uncertainty = risk…
Volatility has increased Price (& capital requirement) goes up
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The data is out there
climatechange.pbwiki.com/DataSources
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Specific areas of uncertainty
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Areas we will cover
Sensitivity testingData considerationsInsurance riskCredit riskOperational riskMarket riskStress and scenario tests
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Sensitivity testing
How does parameter uncertainty apply here? Identification of key parametersWhat is the impact of changing key parametersCorrelation levelsCommunication – separating theory and practical implementation
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Data considerations
Are there different / new data considerations in the ICA environment, compared to reserving?Data outliersWhat is the impact of one year of extra data?
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Insurance risk
ObservationsBest practice splits underwriting risk, reserve risk and reinsurance riskUnderwriting risk can be further split between claims risks and pricing risksClaims risks can be further split between attritional losses, large losses and catastrophic losses
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Insurance risk
Reserve riskAllowing ultimate reserve uncertainty to emerge
Need to allow for relevant reinsurance?When is bootstrapping paid claims a reasonable approach to estimating reserve risk?
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Insurance risk
Underwriting riskSeparating underlying attritional loss ratio volatility from pricing volatilityWhat is a ‘1 in 200’ level of catastrophe?What is the uncertainty surrounding this?What is a ‘1 in 200’ level of large loss?
What is a ‘1 in 200’ motor large loss?
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Insurance risk
Long tailed lines of business / liability businessWhat is the appropriate amount of uncertainty to allow for when considering long tailed liability account reserves, eg AsbestosWhat allowance should be made for future latent claims?
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Credit risk
Which things need consideration?Investment credit riskCounterparty credit risk
Where does materiality let us stop? Allowance for reinsurance credit risk ‘to ultimate’ Ripple effects - Increased risk following major insurance event
(increase in probability and exposure)How to treat ‘binary’ events
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Operational risk
‘Most operational risks eventually manifest themselves within historic (claims) data – our parameterisation includes Op risk implicitly’
Is this a reasonable claim?Use of risk registers to populate stress test models of Op riskDefined benefit pension scheme ICA requirementIs a simple percentage loading for Op risk reasonable?Avoiding double counting / excessive prudence
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Market risk
Valuation basisAllowance for discountingParameter uncertaintyMarket consistencyUse of an ESG versus self derived modelsInvestment policy – designed for which basis?Materiality
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Stress and scenario tests
Typical use – stress tests to derive capital requirement, scenario tests for testingEnsuring consistency between probabilities for different stress testsEvaluation of expected and maximum costs for stress tested eventsWhat is a reasonable objective when using stress testsUse of model output to inform stress/scenario testsAggregation of stress test results