In Sari Ropponen’s SHV-thesis ’Kollektiivinen korvausvastuu’ the calculation of IBNR-reserves is described using various methods. In this paper, the calculation of IBNR-reserves is expanded to include credibility methods, which are not addressed in Ropponen’s thesis. The purpose of this paper is, in addition to presenting the theory, to provide the reader with examples, so that practical implementation of the methods presented is effortless.

The beginning briefly covers credibility theory and Bühlmann’s model. Following this, three methods based on credibility theory are presented for calculating IBNR-reserves based on a run-off triangle. A run-off triangle, also known as a claims triangle, is a tool to track the development of insurance claims over time. The methods presented are De Vylder’s method, Hadidi’s method, and Mack’s method. For each method, the model is discussed in general, and additionally, how estimation of required parameters can be performed.

In the final chapter of the paper, the amount of IBNR-reserves is calculated using the methods presented earlier. Every method is using the same run-off triangle as its input data. The calculations are detailed so that the reader can easily apply the theory presented earlier in practice. Finally, the results obtained from different methods are compared with each other.

From the examples in the paper, it is noticeable that different methods yield results that are close to each other. However, Hadidi’s method provides the insurance company with means to conduct sensitivity analyses of IBNR-reserves using credibility methods.

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