The Path of the Ultimate Loss Ratio Estimate

By Michael G. Wacek

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Abstract

This paper presents a framework for stochastically modeling the path of the ultimate loss ratio estimate through time from the inception of exposure to the payment of all claims. The framework is illustrated using Hayne’s lognormal loss development model, but the approach can be used with other stochastic loss development models. The behavior of chain ladder and Bornhuetter-Ferguson estimates consistent with the assumptions of Hayne’s model is examined. The general framework has application to the quantification of the uncertainty in loss ratio estimates used in reserving and pricing as well as to the evaluation of risk-based capital requirements for solvency and underwriting analysis.

KEYWORDS: Stochastic model, diffusion process, loss development, loss ratio estimation, lognormal, Student's t, log t, parameter uncertainty

Citation

Wacek, Michael G., "The Path of the Ultimate Loss Ratio Estimate," Variance 1:2, 2007, pp. 173-192.

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Variance is a peer-reviewed journal published by the Casualty Actuarial Society to disseminate work of interest to casualty actuaries worldwide. The focus of Variance is original practical and theoretical research in casualty actuarial science. Significant survey or similar articles are also considered for publication. Membership in the Casualty Actuarial Society is not a prerequisite for submitting papers to the journal and submissions by non-CAS members is encouraged.