Equity and Credibility

We build on previous work concerned with measuring equity and consider the problem of using observed claim data or other information to calculate premiums which maximize equity. When these optimal premiums are used, we show that gathering more information or refining the risk classification always increases equity. We study the case for which the premium is constrained to be an affine function of the claim data and obtain results analogous to classical credibility theory, including the inhomogeneous and homogeneous cases of the Bu¨hlmann-Straub model. We derive formulas for the credibility weights in certain cases.     

Risk-adjusted credibility premiums using distorted probabilities

Abstract

Denneberg (1990) and Wang (1996a) propose that one calculate risk-adjusted insurance premiums as the expectation with respect to a distorted probability measure, a non-additive set function. This premium principle is supported by the theories of decision making of Yaari (1987) and of Schmeidler (1989). Denneberg (1994a) presents three conditioning rules for updating non-additive set functions in light of available information. In this work, we show how to apply these three update rules to calculate a risk-adjusted credibility premium and, thereby, combine credibility theory with this relatively new premium principle. Our main result is that, for some pairs of distortion function and update rule, one gets the same risk-adjusted credibility premium by distorting the predictive probability distribution, as required by the theory of Yaari, or by updating the distorted probability, as required by the theory of Schmeidler.     

An Actuarial Analysis of Participating Life Insurance

An actuarial model is developed to reveal the intrinsic nature of participating life insurance. The basic safe-side criterion is examined. It is established how the first-order prospective net premium reserve includes safety margins or bonus loadings, and it is demonstrated how the bonus loadings are currently released. It is demonstrated how surplus may be distributed and accumulated as a terminal bonus in an equitable way. The level premium is divided into a variable recurrent single premium and a variable natural premium, and an alternative to the prospective net premium reserve is examined. A capitalization of future safety margins or bonus loadings, which are related to past premiums and the paid-up benefit, may allow the insurance company a considerable increase in investment freedom. The theory is illustrated by numerical results.     

The pricing of capital assets in a multiperiod world

This paper proposes a general framework for the pricing of capital assets in a multiperiod world. Under quite general conditions, the analysis shows that the equilibrium expected nominal return on any asset can always be expressed as the sum of the risk-free rate and various risk premiums. The first risk premium is identical to the usual risk premium in the Sharpe-Lintner-Mossin capital asset pricing model. The mathematical forms of all the remaining risk premiums are identical even though each individual risk premium may be present for a different reason.     

Heterogeneous Premiums for Homogeneous Risks? Asset Liability Management under Default Probability and Price-Demand Functions

We consider an asset liability model under an internal solvency constraint that includes default probability as well as price-demand functions and combine insights from empirical and theoretical research. Furthermore, as a result of policyholders’ heterogeneous willingness to pay, we introduce heterogeneous premiums to maximize the insurer’s overall net present value and compare the results with an optimal homogeneous premium. To determine a reservation price for the insurer, we use the Margrabe-Fischer option-pricing formula. Our numerical examples document that heterogeneous premiums for homogeneous risks improve the net present value when correct expectations underlie and are vulnerable against a cost shift but do not per se induce a decrease in the net present value. Moreover, we recognize that the optimal price setting under overall net present value maximization varies from the underwriting net present value maximization on the individual risk level. Hence, in practice, an overall asset liability management perspective should be in focus to reach the best results from the company’s point of view.     

E. J. Moorhead (1910 – 2004)

Abstract

As is well known in actuarial practice, excess claims (outliers) have a disturbing effect on the ratemaking process. To obtain better estimators of premiums, which are based on credibility theory, Künsch and Gisler and Reinhard suggested using robust methods. The estimators proposed by these authors are indeed resistant to outliers and serve as an excellent example of how useful robust models can be for insurance pricing. In this article we further refine these procedures by reducing the degree of heuristic arguments they involve. Specifically we develop a class of robust estimators for the credibility premium when claims are approximately gamma-distributed and thoroughly study their robustness-efficiency trade-offs in large and small samples. Under specific datagenerating scenarios, this approach yields quantitative indices of estimators’ strength and weakness, and it allows the actuary (who is typically equipped with information beyond the statistical model) to choose a procedure from a full menu of possibilities. Practical performance of our methods is illustrated under several simulated scenarios and by employing expert judgment.     

Incorporating the Bühlmann credibility into mortality models to improve forecasting performances

In this paper, we incorporate the Bühlmann credibility into three mortality models (the Lee–Carter model, the Cairns–Blake–Dowd model, and a linear relational model) to improve their forecasting performances, as measured by the MAPE (mean absolute percentage error), using mortality data for the UK. The results show that the MAPE reduction ratios for the three mortality models with the Bühlmann credibility are all significant. More importantly, the MAPEs under the three mortality models with the Bühlmann credibility are very close to each other for each age and forecast year. Thus, by incorporating the Bühlmann credibility we are able to converge the forecasting MAPEs resulting from the three different mortality models to a lower and more consistent level. Moreover, we provide a credibility interpretation with an individual time trend for age x and a group time trend for all ages. Finally, we apply the forecasted mortality rates both with and without the Bühlmann credibility to the net single premiums of life insurance products, and compare the corresponding MAPEs.     

Premiums and reserves,adjusted by distortions

The net premium principle is considered to be the most genuine and fair premium principle in actuarial applications. However, actuarial due diligence requires additional caution in pricing of insurance contracts to avoid, for example, at least bankruptcy of the insurer. This paper addresses the distorted premium principle from various angles. Distorted premiums are typically computed by underweighting or ignoring low, but overweighting high losses. Dual characterizations, which are elaborated in a first part of the paper, support this interpretation. The main contribution consists in an opposite point of view—an alternative characterization—which leaves the probability measure unchanged, but modifies (increases) the outcomes instead in a consistent way. It turns out that this new point of view is natural in actuarial practice,as it can be used for premium calculations, but equally well to determine the reserve process in subsequent years in a time consistent way.     

Zur Bedeutung der sekundären Prämiendifferenzierung bei Unisex-Tarifen in der Krankenversicherung

In the German and European legislation there is a trend to prohibit gender-based premiums in the private insurance sector. Compared with other insurance sectors the private health insurance can not only differentiate the premiums ex ante but also ex post (secondary premium differentiation). A change in ex ante differentiation must result in a change in ex post differentiation. It is shown that an extended secondary premium differentiation can compensate the effects of the prohibition of gender-based premiums if we consider not only the premiums but also premium refunds and own contributions.     

Ursachen geschlechtsspezifischer Kostenunterschiede in der Privaten Krankenversicherung: Eine empirische Untersuchung unter besonderer Berücksichtigung der Anforderungen des AGG

The new “Allgemeine Gleichbehandlungsgesetz” (General Equal Treatment Act) also influences the premium calculation of the German Private Health Insurance to antagonize gender discrimination in premiums. The higher premiums in the Private Health Insurance women pay are caused by higher expectation of life, by the risk of fertility, and by higher individual health-care costs for health services. We study how strong the gender influence in health-care costs of men and women are and if they are influenced by the factors mentioned above. We analyse if there is any gender discrimination in premium calculation in the Private Health Insurance. The results show that after eliminating the factors only a small reduction of premiums is found. We still find a cost difference between women and men. This difference can be explained by the different usage of health services but this depends less on the gender rather on individual psychosocial factors.     

Credibility for Severity Revisited

Abstract

It is basic actuarial knowledge that the pure premium of an insurance contract can be written as the product of the expected claim number and the expected claim amount. Actuaries use credibility theory to incorporate the contract’s individual experience into this calculation in a statistically optimal way. For many years, however, the use of credibility was limited to the frequency component. Starting with the paper by Hewitt (1971), there have been various suggestions as to how credibility theory also can be applied to the severity component of the pure premium. The latest such suggestion, Frees (2003), revived the interest in the problem.

In this paper, we review four different formulas incorporating frequency and severity into credibility calculations. We then compare by simulation which one is most accurate at predicting a contract’s next-year outcome. It is found that the classical formula of Bühlmann (1967) is as good as the other ones in many cases. Alternatives, however, may offer easier analysis of the separate effects of frequency and severity on the premium.

We also show that all the formulas reviewed in this paper stem from the same minimization problem, and we present a general, integrated, solution. At the same time, we complete Gerber (1972) by providing a proof to the main result of this paper and by stating required additional assumptions.     

Optimal proportional reinsurance with a loss-dependent premium principle

ABSTRACT

Empirical studies suggest that many insurance companies recontract with their clients on premiums by extrapolating past losses: a client is offered a decrease in premium if the monetary amounts of his claims do not exceed some prespecified quantities, otherwise, an increase in premium. In this paper, we formulate the empirical studies and investigate optimal reinsurance problems of a risk-averse insurer by introducing a loss-dependent premium principle, which uses a weighted average of history losses and the expectation of future losses to replace the expectation in the expected premium principle. This premium principle satisfies the bonus-malus and smoothes the insurer's wealth. Explicit expressions for the optimal reinsurance strategies and value functions are derived. If the reinsurer applies the loss-dependent premium principle to continuously adjust his premium, we show that the insurer always needs less reinsurance when he also adopts this premium principle than when he adopts the expected premium principle.     

Prämienkalkulation und die „Sanierung“ von Versicherungsverträgen

For assessing the risk adjusted insurance premiums, we always face the challenge that we don’t know the respective distribution functions of the probable claims and the probability of occurrence. Purely chance-based deviations from expected damages are no sufficient reason for premium increases. This means that for preparing for such deviations we have to distinct between chance-based and other deviations from expected and realised damage events. For adjusting insurance contracts due to new information, there are three possible strategies: first, we could ignore the past premium and calculate them based on the new data sample. Alternatively we could make use of a Bayesian learning process, which means to adjust the past premiums by taking into account the new information. The third strategy refers to a statistical test of hypotheses. This means to only adjust a premium if the original assumptions on the possible distribution of claims have to be rejected statistically. Looking at the certainty of the contracts and a steady calculation basis, there are many reasons in favour of the statistical test of hypotheses. The stringent usage of this method can lead to a sound basis for negotiations between insurance provider and holder. The improvement of transparency of taken risks is regulatorily desirable as well as helpful for evaluation of solvency.     

How is illiquidity priced in the Chinese stock market?

This study investigates the liquidity premium in the Chinese stock market. We found that the expected stock returns increase monotonically with the quintile sort on characteristic liquidity with descending patterns. The characteristic liquidity premium ranges from 0.82% to 1.28% per month, which is much higher than that of their US counterparts. Moreover, our multivariate decomposition approach highlights that characteristic illiquidity premiums can be explained mainly by size, idiosyncratic volatility and momentum. The net systematic liquidity premium reaches 0.84% per month, driven mainly by commonality beta. The finding shows that a liquidity-based strategy forecasts cross-section and time-series expected returns.     

Simultaneous borrowing of information across space and time for pricing insurance contracts: An application to rating crop insurance policies

Changing climate and technology can often lead to nonstationary losses across both time and space for a variety of insurance lines including property, catastrophe, health, and life. As a result, naive estimation of premium rates using past losses will tend to be biased. We present three successively flexible data‐driven methodologies to nonparametrically smooth across both space and time simultaneously, thereby appropriately incorporating possibly nonidentically distributed data into the rating process. We apply these methodologies in estimating U.S. crop insurance premium rates. Crop insurance, with global premiums totaling $4.1 trillion in 2018, is an interesting application as losses exhibit both temporal and spatial nonstationarity. We find significant borrowing of information across both time and space. We also find all three methodologies improve both the stability and accuracy of crop insurance premium rates. The proposed methods may be of relevance for other lines of insurance characterized by spatial and/or temporal nonstationary losses.     

Investigating the stationarity of insurance premiums: international evidence

This article explores whether there is support for the stationarity hypotheses of life and non-life insurance premiums during the period 1979–2007 for 40 heterogeneous countries. The stationarity of insurance premiums affects insurance companies’ prediction on their future inflow of premium income, which affects the liquidity of insurance companies and their investment plans and thus is relevant to the insurers’ operation. This article employs the advanced nonlinear panel unit-root test with a sequential panel selection method to classify the entire panel into two groups: stationary countries and non-stationary countries. We apply Monte Carlo simulations to derive empirical distributions of the test, which allows us to correct for the finite-sample bias and to consider the cross-country effects. We find relatively stationary life insurance premiums in countries from the following groups: high-income, Europe, and common law origin; relatively stationary non-life insurance premiums exist in the following groups: low-income, Middle East and Africa, and common law origin. Evidence herein shows that different classifications, including income levels, geographic regions, regionally or economically integrated blocs, and legal system, affect the stationarity of life and non-life insurance premiums.     

Social connections,reference point and acquisition premium

This paper examines the impact of acquirer-target social connections along with the target 52-week high (Baker et al., 2012) on acquisition premiums. We show that acquisition premium is more sensitive to first-degree connection than the reference point, suggesting that information is the main driving force for determining acquisition premiums. The findings also indicate that connected directors are more likely to favour firms where they hold higher positions and negotiate favourable premiums. Acquirers pay lower premiums when target directors are retained in the new entity. Connected acquirers are also more likely to finance their deals with equity. Overall, this paper provides support to the information flow hypothesis that acquirers with social connections have better access to target information and enhanced bargaining power in negotiations.     

Negotiating contract types and contract clauses in the German construction industry during the Third Reich

This article examines the determinants of contractual form and renegotiations in the German construction industry during the Third Reich. At the beginning of World War II, firms dealt with growing uncertainty by convincing procurement agencies either to use cost‐plus contracts or to include an additional risk premium in fixed‐price contracts. In the later years of the war, procurement agencies initiated renegotiations over contract clauses to reduce the extraordinary profits resulting from information rents and high‐risk premiums. This regulatory course undermined the credibility of the regulatory commitment, thereby weakening the incentives of the fixed‐price contracts still in use.     

Closed‐End Fund Discounts and Expected Investment Performance

This article provides empirical support for the theory that closed‐end fund discounts reflect expected investment performance. Evidence is presented to explain how equity closed‐end fund initial public offerings (IPOs) can sell at a premium when existing funds sell at a discount and why the initial IPO premiums decay after the IPO. Relative premium decay data are presented. Tests on (1) the relation between relative premium changes and investment performance following IPOs, (2) relative premium mean‐reversion following management changes, and (3) net redemptions following closed‐end fund open‐endings for funds trading at pre‐open‐ending announcement discounts individually support and collectively strongly support the theory.     

Bayesian and Bühlmann credibility for phase-type distributions with a univariate risk parameter

Credibility theory is a statistical tool to calculate the premium for the next period based on past claims experience and the manual rate. Each contract is characterized by a risk parameter. A phase-type (or PH) random variable, which is defined as the time until absorption in a continuous-time Markov chain, is fully characterized by two sets of parameters from that Markov chain: the initial probability vector and transition intensity matrix. In this article, we identify an interpretable univariate risk parameter from amongst the many candidate parameters, by means of uniformization. The resulting density form is then expressed as an infinite mixture of Erlang distributions. These results are used to obtain a tractable likelihood function by a recursive formula. Then the best estimator for the next premium, i.e. the Bayesian premium, as well as its approximation by the Bühlmann credibility premium are calculated. Finally, actuarial calculations for the Bühlmann and Bayesian premiums are investigated in the context of a gamma prior, and illustrated by simulated data in a series of examples.