Loss Models: From Data to Decisions, 4th Edition
by Stuart A. Klugman, Harry H. Panjer, Gordon E. Willmot
7.4 Effect of exposure on frequency
Assume that the current portfolio consists of n entities, each of which could produce claims. Let Nj be the number of claims produced by the jth entity. Then N = N1 + ··· + Nn. If we assume that the Njs are independent and identically distributed, then
![]()
Now suppose the portfolio is expected to expand to n* entities with frequency N*. Then
![]()
Thus, if N is infinitely divisible, the distribution of N* will have the same form as that of N, but with modified parameters.
EXAMPLE 7.18
It has been determined from past studies that the number of workers compensation claims for a group of 300 employees in a certain occupation class has the negative binomial distribution with β = 0.3 and r = 10. Determine the frequency distribution for a group of 500 such individuals.
The pgf of N* is
![]()
which is negative binomial with β = 0.3 and r = 16.67.
For the (a, b, 0) class, all members except the binomial have this property. For the (a, b, 1) class, none of the members do. For compound distributions, it is the primary distribution that must be infinitely divisible. In ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access