Replicated Stratified Sampling

Replicated Stratified Sampling

A Practical Approach to Financial Modeling

2010 IABA Annual Meeting

August 6 - 7, 2010

Jay Vadiveloo, PhD, FSA, MAAA,CFA

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Notice

This presentation has been prepared solely for informational purposes and Towers Watson does not make any representation or warranty, either express or implied, as to the accuracy, completeness or reliability of the information contained in this presentation.

Your organization should consult its own counsel, tax, actuarial and financing advisors as to legal and other matters concerning any of the material presented herein.

Towers Watson expressly disclaims any and all liability relating or resulting from the use of this presentation.

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Background

Actuarial valuation of insurance liabilities typically involves production –based, seriatim calculations.

Today’s insurance products include complex features with investment oriented characteristics that require stochastic modeling of market and interest rate performance.

Commercial actuarial software has been designed to handle large, complex stochastic modeling of insurance liabilities.

In most actuarial analyses, for both regulatory and management purposes, the focus is on the risk exposure at the tails (typically the 90th percentile and beyond).

Long run times and lack of a management tool for what-if, actionable analysis.

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Solutions from several sources have been explored

Actuarial

Methods

 Scenario reduction

 Modeling/compression

Advantages

 Familiar and well-understood

Disadvantages

 Reduces accuracy

 Exposed to model risk

 Run-time savings not sufficient

Technological

Methods

 Grid processing

Advantages

 Brute force method so easy to understand

 Can always buy more computers

Disadvantages

 Costly

 Battle for grid time

 Still long run times

Market-driven

Methods

 Replicating portfolios towerswatson.com

Advantages

 Closed-form solutions so extremely fast

 Allows processing of many scenarios

Disadvantages

 Only works for market-based parameters – can’t analyze mortality or lapse scenarios

 Fit to insurance liabilities

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Statistical Sampling Approaches

Non-existent in actuarial modeling techniques!

Why?

Availability

Entire population

Detailed policy information

Leads to seriatim calculations or grouping methods

Perception that more detail is always better

Analysis of entire population gives more precise information than analysis of a random sample

Sampling error difficult to quantify

Lacking a bridge between academia and industry

UConn Actuarial Center is that bridge towerswatson.com

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Towers Watson Replicated Stratified Sampling (RSS)

Our patent-pending approach rapidly accelerates run times for many actuarial models, and has the following characteristics:

Based on sound fundamentals of statistical inference

Combination of stratified sampling and sample replication

Reduces run time for any complex stochastic model

 with large underlying population

 with easy access to underlying population

Produces stable results

Produces robust results with measurable, pre-determined sampling error

Simple to understand, implement and maintain towerswatson.com

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Uniqueness of the RSS Approach

Does not attempt to “simplify” or “approximate” the underlying population characteristics.

Builds on the existing company actuarial models.

Allows for detailed analysis of cash flows under both economic scenarios (equity and interest rate changes) and changes in actuarial assumptions (mortality, lapses, policyholder behavior, etc).

The entire underlying population distribution is approximated under

RSS at a prescribed level of accuracy for each quantile.

Convergence time is independent of the size of the population.

Convergence speed and accuracy of RSS technique are based on wellestablished and tested statistical inference theory.

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RSS Pilot Study

RSS technique applied to a variable annuity block of a major life insurance company.

Analyzed impact of

- an immediate 15% drop in equity funds on VACARVM reserves

- an immediate 3 5% drop in equity funds on VACARVM reserves

Analysis done for 3 legal entities both before and after reinsurance .

Analysis compared the change in the VACARVM reserve in the population versus using the RSS technique on 50, 100, 150 and 200 samples of 30 policies each.

A

B

Error rate defined as:

B where A = change in VACARVM reserve using the RSS technique

B = change in VACARVM reserve in the population towerswatson.com

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Legal

Entity

1

2

3

Population Summary

After Reinsurance

Number of policies

Baseline

Reserves

1,027,572 -2,765,845

397,781 -13,298,401

547,883 -3,470,570

Sensitivity 1

Reserves

-4,605,188

-19,171,991

-12,610,502

Sensitivity 2

Reserves

-11,714,900

-20,009,138

-87,276,482

POP

Ratio 1

1.665

1.442

POP

Ratio 2

4.236

1.505

3.634

25.148

Legal

Entity

1

2

3

Number of policies

Before Reinsurance

Baseline

Reserves

Sensitivity 1

Reserves

1,027,572 -79,535,358 -168,055,144

Sensitivity 2

Reserves

-582,368,081

397,781 -890,538,871 -1,621,720,896 -3,807,237,541

547,883 -8,777,155 -27,902,521 -178,654,004

POP

Ratio 1

2.113

1.821

3.179

POP

Ratio 2

7.322

4.275

20.354

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Legal

Entity

1

2

3

RSS Results – Sensitivity 1

After Reinsurance Before Reinsurance

Legal

Entity

# Of samples

50

100

150

200

50

100

150

200

50

100

150

200

RSS

Ratio

POP

Ratio

Error

Rate

1.513

1.665

9.14%

1.615

3.00%

1.640

1.52%

1.667

0.12%

1.611

1.442

11.73%

1.486

1.424

3.10%

1.25%

1.450

0.59%

3.015

3.634

17.02%

3.482

3.735

3.633

4.18%

2.78%

0.02%

1

2

3

# Of samples

50

100

150

200

50

100

150

200

50

100

150

200

1.818

1.822

2.853

3.028

3.153

3.177

RSS

Ratio

2.067

2.124

2.106

2.110

1.826

1.812

POP

Ratio

2.113

1.821

0.17%

0.03%

3.179

10.24%

4.74%

0.82%

0.07%

Error

Rate

2.17%

0.51%

0.32%

0.15%

0.25%

0.49% towerswatson.com

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Legal

Entity

1

2

3

RSS Results – Sensitivity 2

After Reinsurance Before Reinsurance

Legal

Entity

# Of samples

50

100

150

200

50

100

150

200

50

100

150

200

RSS

Ratio

POP

Ratio

Error

Rate

2.771 4.236 34.58%

3.783 10.68%

4.071

4.216

3.88%

0.45%

1.117 1.505 25.75%

1.339 11.00%

1.386

1.506

7.89%

0.10%

17.574 25.148 30.12%

23.239

26.601

25.225

7.59%

5.78%

0.31%

1

2

3

# Of samples

50

100

150

200

50

100

150

200

50

100

150

200

RSS

Ratio

POP

Ratio

Error

Rate

5.575 7.322 23.86%

7.043

7.099

7.330

3.81%

3.04%

0.10%

4.884 4.275 14.24%

5.117 19.70%

4.652

4.282

8.81%

0.15%

13.845 20.354 31.98%

19.059 6.37%

21.203 4.17%

20.336 0.09% towerswatson.com

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Advantages of the RSS Approach

Significantly reduces run time, allowing more flexibility and transparency in trade-offs between speed and accuracy:

Increase accuracy

Run more stochastic scenarios, improving tail risk analysis

Reduce use of grouping techniques, improving risk analysis in general

Reduce use of shortcuts in modeling approach, decreasing model risk

Map complex investment funds directly, eliminating basis risk

Minimize sampling bias

Increase speed

Maintain model and population complexity but decrease run time

Broad Applicability

Can be used across a range of models and calculations towerswatson.com

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Potential Applications of the RSS Approach

U.S. GAAP

SFAS 133, SOP 03-1

Production, impact testing, forecasting

VACARVM

Production, impact testing, attribution analysis

Economic

Strategic Planning

Capital

Hedge Programs

Hedge effectiveness testing, Explanation of breakage

PBA for life insurance products

Analysis of Inforce

Profitability

Any type of analysis that relies on complex, stochastic calculations is a candidate for the RSS approach towerswatson.com

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RSS as a Strategic Management Tool

RSS is ideally suited for any type of “what if” management analysis

Instead of 1,000 scenarios, run 10,000 or 100,000

Instead of 5 or 10 sensitivities, run 50, 100, or 500

Results are more robust, more accurate, more timely and therefore more actionable

Using RSS, management can be prepared for so called 4 th quadrant (low probability, high severity) events that threaten the long-term sustainability of the insurance industry.

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Open Analytical Research Topics

Mathematical proof, using existing convergence theorems in statistics, that the RSS algorithm generates unbiased and efficient estimates of the change in the population risk measure and is independent of the underlying risk measure being analyzed.

Analytical justification, using numerical analysis and asymptotic techniques, on the number of replications required to achieve a prescribed accuracy level of the RSS estimate of the change in the population risk measure.

Use of clustering analysis techniques to determine the optimal set of risk classes in order to minimize processing time subject to a prescribed level of accuracy of the RSS estimates.

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Conclusions

Complex actuarial modeling in response to increasingly complex insurance products has led to run times that are prohibitive.

To cope, management has been forced to make trade-offs that are costly either in speed, accuracy or dollar costs.

Towers Watson’s Replicated Stratified Sampling (RSS) approach offers a paradigm shift in measuring and managing risk using actuarial modeling, by dramatically reducing run time for:

Stochastic models, including hedging tools,

Models with large databases,

Models with easy access to underlying population.

The RSS approach allows management more flexibility to proactively participate in the risk management process and better understand the impact of current and potential market, economic, actuarial and customer behavior changes.

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Contact details

Jay Vadiveloo, PhD, FSA, MAAA, CFA

Towers Watson Consulting Actuary

Towers Watson Professor, University of Connecticut

Work: (860) 843-7073

Cell: (860) 916-1010

Email: Jay.Vadiveloo@towerswatson.com towerswatson.com

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