Determination of Insurance Premiums Using The Optimal Bonus-Malus System with The Bayesian Method

Authors

  • Fatichatu Zahro Sunan Kalijaga State Islamic University Yogyakarta image/svg+xml
  • Sri Istiyarti Uswatun Chasanah Sunan Kalijaga State Islamic University Yogyakarta image/svg+xml
  • Syarif Abdullah Sultan Ageng Tirtayasa University image/svg+xml

DOI:

https://doi.org/10.14421/kaunia.5462

Keywords:

Bayesian Method, Bonus–Malus System, Poisson Distribution, Exponential Prior, Beta Prior

Abstract

This study develops an optimal bonus–malus premium model within a Bayesian decision-theoretic framework. Claim frequency is modeled using a Poisson distribution, while the number of claims exceeding a predefined critical threshold is modeled conditionally using a Binomial distribution. The Poisson intensity parameter is assigned an Exponential prior distribution, while the Binomial probability parameter follows a Beta prior distribution. The Exponential and Beta distributions are applied to model parameters rather than to observed data, ensuring probabilistic consistency. Since the Exponential distribution is a special case of the Gamma distribution, the Bayesian updating process remains mathematically coherent. To illustrate the model, a dataset of 1,000 simulated motor vehicle policyholders is generated in R under specified distributional assumptions. The results indicate that premiums increase with the number of claims exceeding the critical value and decrease with longer claim-free duration. The proposed framework provides a coherent and flexible approach for premium determination in bonus–malus systems. However, the findings are based on simulated data and specific modeling assumptions, which may limit direct empirical generalization.

 

References

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Published

2026-03-13

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Section

Articles

How to Cite

Determination of Insurance Premiums Using The Optimal Bonus-Malus System with The Bayesian Method. (2026). Kaunia: Integration and Interconnection Islam and Science Journal, 21(2), 101-108. https://doi.org/10.14421/kaunia.5462