Claim Size Distribution Research Articles

The Gerber-Shiu function for the compound Poisson Omega model with a three-step premium rate

The compound Poisson Omega model is considered in the presence of a three-step premium rate. Firstly, the integral equations and the integro-differential equations for the Gerber-Shiu expected discounted penalty function are derived. Secondly, the integro-differential equations for the Gerber-Shiu expected discounted penalty function are determined in three different initial conditions. The results are then used to find the bankruptcy probability. Finally, the special cases where the claim size distribution is exponential be discussed in some detail in order to illustrate the effect of the model with three-step premium rate.

Ruin probabilities under capital constraints

In this paper, we generalise the classic compound Poisson risk model, by the introduction of ordered capital levels, to model the solvency of an insurance firm. A breach of the higher capital level, the magnitude of which does not cause further breaches of either the lower level or the so-called intermediate confidence level (of the shareholders), requires a capital injection to restore the surplus to a solvent position. On the other hand, if the confidence level is breached capital injections are no longer a viable method of recapitalisation. Instead, the company can borrow money from a third party, subject to a constant interest rate, which is paid back until the surplus returns to the confidence level and subsequently can be restored to a fully solvent position by a capital injection. If at any point the surplus breaches the lower capital level, the company is considered ‘insolvent’ and is forced to cease trading. For the aforementioned risk model, we derive an explicit expression for the ‘probability of insolvency’ in terms of the ruin quantities of the classical risk model. Under the assumption of exponentially distributed claim sizes, we show that the probability of insolvency is in fact directly proportional to the classical ruin function. It is shown that this result also holds for the asymptotic behaviour of the insolvency probability, with a general claim size distribution. Explicit expressions are also derived for the moment generating function of the accumulated capital injections up to the time of insolvency and finally, in order to better capture the reality, dividend payments to the companies shareholders are considered, along with the capital constraint levels, and explicit expressions for the probability of insolvency, under this modification, are obtained.

Asymptotic ruin probabilities for a bidimensional risk model with heavy-tailed claims and non-stationary arrivals

This article studies a bidimensional risk model, in which an insurer simultaneously confronts two kinds of claims sharing a common non-stationary arrival process. Assuming that the arrival process satisfies a large deviation principle and the claim-size distributions are heavy tailed, an asymptotic formula for the corresponding ruin probability of this bidimensional risk model is obtained.

Upper bounds for ruin probabilities under model uncertainty

In this paper, we investigate some ruin problems for risk models that contain uncertainties on both claim frequency and claim size distribution. The problems naturally lead to the evaluation of ruin probabilities under the so-called G-expectation framework. We assume that the risk process is described as a class of G-compound Poisson process, a special case of the G-Lévy process. By using the exponential martingale approach, we obtain the upper bounds for the two-sided ruin probability as well as the ruin probability involving investment. Furthermore, we derive the optimal investment strategy under the criterion of minimizing this upper bound. Finally, we conclude that the upper bound in the case with investment is less than or equal to the case without investment.

Focussed selection of the claim severity distribution

ABSTRACTRisk assessment is a core theme within non-life insurance and estimation of quantiles far out in the upper tail is therefore one of the main applications of the total loss distribution of a non-life insurance portfolio. The choice of claim severity distribution should therefore reflect this. Therefore, we have explored how the focussed information criterion, FIC, aimed at finding the best model for estimating a given parameter of interest, the focus parameter, works as a tool for selecting the claim size distribution. As a quantile cannot be used directly as a focus parameter, we have tried different proxy focus parameters. To see how the FIC performs in this setting, compared to the other commonly used model selection methods AIC and BIC, we have performed a simulation study. In particular, we wanted to investigate the effect of the heaviness of the tail of the claim size distribution and the amount of available data. The performance of the different model selection methods was then evaluated based on the quality of the resulting estimates of the quantiles. Our study shows the best of the focussed criteria is the FIC, based on one single quantile from the claim severity distribution. Further, the performance of the FIC is mostly either comparable to or considerably better than that of the BIC, which is the best performing of the state of the art approaches. In particular, the FIC works well when the data are heavy-tailed, when the sample size is rather low and when the parameter of interest is the quantile far out in the tail of the total loss distribution.

Parisian types of ruin probabilities for a class of dependent risk-reserve processes

ABSTRACTFor a rather general class of risk-reserve processes, we provide an exact method for calculating different kinds of ruin probabilities, with particular emphasis on variations over Parisian type of ruin. The risk-reserve processes under consideration have, in general, dependent phase-type distributed claim sizes and inter-arrivals times, whereas the movement between claims can either be linear or follow a Brownian motion with linear drift. For such processes, we provide explicit formulae for classical, Parisian and cumulative Parisian types of ruin (for both finite and infinite time horizons) when the clocks are phase-type distributed. An erlangization scheme provides an efficient algorithmic methods for calculating the aforementioned ruin probabilities with deterministic clocks. Special attention is drawn to the construction of specific dependency structures, and we provide a number of numerical examples to study its effect on probabilities.

On a two-dimensional risk model with time-dependent claim sizes and risky investments

Consider a two-dimensional risk model, in which two insurance companies divide between them the claims in some specified proportions. Suppose that the claim sizes and inter-arrival times form a sequence of independent and identically distributed random pairs, with each pair obeying a dependence structure, and the surpluses of the two companies are invested into portfolios whose returns follow two different geometric Lévy processes. When the claim-size distribution is extended-regularly-varying tailed, asymptotic expressions for the ruin probability of this two-dimensional risk model are exhibited. Some numerical results are also presented to illustrate the accuracy of our asymptotic formulae.

ON THE EVALUATION OF MULTIVARIATE COMPOUND DISTRIBUTIONS WITH CONTINUOUS SEVERITY DISTRIBUTIONS AND SARMANOV'S COUNTING DISTRIBUTION

AbstractIn this paper, we present closed-type formulas for some multivariate compound distributions with multivariate Sarmanov counting distribution and independent Erlang distributed claim sizes. Further on, we also consider a type-II Pareto dependency between the claim sizes of a certain type. The resulting densities rely on the special hypergeometric function, which has the advantage of being implemented in the usual software. We numerically illustrate the applicability and efficiency of such formulas by evaluating a bivariate cumulative distribution function, which is also compared with the similar function obtained by the classical recursion-discretization approach.

Uniform asymptotics for discounted aggregate claims in dependent multi-risk model

ABSTRACTIn this paper, we consider a nonstandard renewal multi-risk model where a company has n types of independent insurance contracts and each contract has some dependent claims and stochastic return. The price process of the investment portfolio is described as a geometric Lévy process. When the claim size distribution belongs to the class of , we can get some asymptotic formulae for the tail probability of n types contracts’ discounted aggregate claims and ruin probabilities, holding uniformly for some finite horizons.

Approximation of ruin probabilities via Erlangized scale mixtures

In this paper, we extend an existing scheme for numerically calculating the probability of ruin of a classical Cramér–Lundbergreserve process having absolutely continuous but otherwise general claim size distributions. We employ a dense class of distributions that we denominate Erlangized scale mixtures (ESM) that correspond to nonnegative and absolutely continuous distributions which can be written as a Mellin–Stieltjes convolution Π⋆G of a nonnegative distribution Π with an Erlang distribution G. A distinctive feature of such a class is that it contains heavy-tailed distributions.We suggest a simple methodology for constructing a sequence of distributions having the form Π⋆G with the purpose of approximating the integrated tail distribution of the claim sizes. Then we adapt a recent result which delivers an explicit expression for the probability of ruin in the case that the claim size distribution is modeled as an Erlangized scale mixture. We provide simplified expressions for the approximation of the probability of ruin and construct explicit bounds for the error of approximation. We complement our results with a classical example where the claim sizes are heavy-tailed.

Ruin probabilities in classical risk models with gamma claims

In this paper, we provide three equivalent expressions for ruin probabilities in a Cramér–Lundberg model with gamma distributed claims. The results are solutions of integro-differential equations, derived by means of (inverse) Laplace transforms. All the three formulas have infinite series forms, two involving Mittag–Leffler functions and the third one involving moments of the claims distribution. This last result applies to any other claim size distributions that exhibits finite moments.

Ruin probabilities in a Sparre Andersen model with dependency structure based on a threshold window

AbstractWe analyse ruin probabilities for an insurance risk process with a more generalised dependence structure compared to the one introduced in Constantinescu et al. (2016). In this paper, we assume that a random threshold window is generated every time after a claim occurs. By comparing the previous inter-claim time with the threshold window, the distributions of the current threshold window and the inter-arrival time are determined. Furthermore, the statuses for the previous and current inter-arrival times give rise to the current claim size distribution as well. Like Constantinescu et al. (2016), we first identify the embedded Markov additive process where all the randomness takes a general form. Inspired by the Erlangisation technique, the key message of this paper is to analyse such risk process using a Markov fluid flow model where the underlying random variables follow phase-type distributions. This would further allow us to approximate the fixed observation windows by Erlang random variables. Then ruin probabilities under the process with Erlang(n) observation windows are proved to be Erlangian approximations for those related to the process with fixed threshold windows at the limit. An exact form of the limit can be obtained whose application will be illustrated further by a numerical example.

The finite-time ruin probability of a discrete-time risk model with GARCH discounted factors and dependent risks

ABSTRACTThe finite-time ruin probability of a discrete-time risk model with dependent stochastic discount factors and dependent insurance and financial risks is investigated in this paper. Assume that the stochastic discount factors follow a GARCH process and the one-period insurance and financial risks form a sequence of independent and identically distributed random pairs, which are the copies of a random pair with a bivariate Sarmanov dependent distribution. When the common distribution of claim-sizes is heavy-tailed, we establish an asymptotic estimate for the finite-time ruin probability. Applying the result to a special case, we also get conservative asymptotic bounds. A numerical simulation is given at the end of the paper.

Large deviations for the stochastic present value of aggregate net claims with infinite variance in the renewal risk model and its application in risk management

In insurance, if the insurer continuously invests her wealth in risk-free and risky assets, then the price process of the investment portfolio can be described as a geometric present Levy process. People always are interested in estimating the tail distribution of the stochastic present value of aggregate claims. In this paper, the large deviation for the stochastic present value of aggregate net claims, when the net claim size distribution is of Pareto type with finite expectation are obtained. We conduct some simulations to check the accuracy of the result we obtained and consider a portfolio optimization problem that maximizes the expected terminal wealth of the insurer subject to a solvency constraint.

Precise Large Deviation of Surplus Processes of Dominatedly-Varying Claims in a Renewal Risk Model

In this paper, we consider a risk model in which the claim sizes are extended negatively associated random variables with dominatedly-varying tails, the arrival of the claims forms a renewal process. and the arrival of the successive insurance policies forms a Poisson process. For this risk model, when the distribution of claim sizes belongs to the intersection of the dominated variation class and subexponential class, we present precise large deviation of the claim surplus process.

A note on the finite-time ruin probability of a renewal risk model with Brownian perturbation

In this note, we consider a renewal risk model with constant force of interest and Brownian perturbation. Assuming that the claim-size distribution function is from the subexponential class, we derive for the finite-time ruin probability a precise asymptotic expansion, which holds uniformly for any finite time horizon. Our result confirms the intuition that the asymptotic ruin probabilities of risk models with heavy-tailed claims are insensitive to the Brownian perturbation.

Densities of Ruin-Related Quantities in the Cramér-Lundberg Model with Pareto Claims

In this paper, we consider the classical yet widely applicable Cramer-Lundberg risk model with Pareto distributed claim sizes. Building on the previously known expression for the ruin probability we derive distributions of different ruin-related quantities. The results rely on the theory of scale functions and are intended to illustrate the simplicity and effectiveness of the theory. A particular emphasis is put on the tail behavior of the distributions of ruin-related quantities and their tail index value is established. Numerical illustrations are provided to show the influence of the claim sizes distribution tail index on the tails of the ruin-related quantities distribution.

Uniform asymptotics for the ruin probabilities of a two-dimensional renewal risk model with dependent claims and risky investments

Consider a two-dimensional renewal risk model, in which the independent and identically distributed claim-size random vectors follow a common bivariate Farlie–Gumbel–Morgenstern distribution. Assuming that the surplus is invested in a portfolio whose return follows a Lévy process and that the claim-size distribution is heavy-tailed, uniformly asymptotic estimates for two kinds of finite-time ruin probabilities of the two-dimensional risk model are obtained.

Asymptotic ruin probabilities for a bidimensional renewal risk model

This paper studies a bidimensional renewal risk model with constant force of interest and heavy-tailed claims. We extend the existing models through allowing arbitrary dependences between each pair of inter-arrival times of the two kinds of insurance claims. A precise asymptotic formula for the finite-time ruin probability is obtained when the claims have subexponential tails. Further restricting the claim-size distributions within the class of extended regular variation, we derive the corresponding asymptotic formula for the infinite-time ruin probability.

The Effects of Largest Claim and Excess of Loss Reinsurance on a Company’s Ruin Time and Valuation

We compare two types of reinsurance: excess of loss (EOL) and largest claim reinsurance (LCR), each of which transfers the payment of part, or all, of one or more large claims from the primary insurance company (the cedant) to a reinsurer. The primary insurer’s point of view is documented in terms of assessment of risk and payment of reinsurance premium. A utility indifference rationale based on the expected future dividend stream is used to value the company with and without reinsurance. Assuming the classical compound Poisson risk model with choices of claim size distributions (classified as heavy, medium and light-tailed cases), simulations are used to illustrate the impact of the EOL and LCR treaties on the company’s ruin probability, ruin time and value as determined by the dividend discounting model. We find that LCR is at least as effective as EOL in averting ruin in comparable finite time horizon settings. In instances where the ruin probability for LCR is smaller than for EOL, the dividend discount model shows that the cedant is able to pay a larger portion of the dividend for LCR reinsurance than for EOL while still maintaining company value. Both methods reduce risk considerably as compared with no reinsurance, in a variety of situations, as measured by the standard deviation of the company value. A further interesting finding is that heaviness of tails alone is not necessarily the decisive factor in the possible ruin of a company; small and moderate sized claims can also play a significant role in this.