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Approximating The Bias And Variance Of Chain Ladder Estimates Under A Compound Poisson Model, Janagan Yogaranpan, Sue Clarke, Shauna Ferris, John Pollard

Journal of Actuarial Practice (1993-2006)

We consider the problem of estimating the outstanding claims produced by a homogeneous general insurance portfolio. The specific model considered in this paper is one where the number of claims in any loss period follows a Poisson distribution, settlement delays follow the same multinomial distribution, and settlements are single lump sums that are independent identically distributed random variables. Simulations using this model reveal that the development ratios and the outstanding claims estimates produced using the chain ladder method are positively biased. We obtain approximate formulas for the biases using Taylor series expansions of the random variables about their means. The …