Change in the balance of homogeneous groups
We might create groups which are more homogeneous (assuming we have sufficient data for credibility), ie in this example at each age have a separate group for workers, office staff and execs. Within each group I can now expect stability with past data being a better reflection of future experience. I may though want just one mortality assumption for each age so I use the results of these analyses to calculate a composite mortality rate for active members of the scheme. I need then to be mindful that the balance of homogeneous groups may change over time, ie could be current makeup of the scheme is 50/30/20 split across the employee categories but that the rate would become inappropriate if the split changed in the future to 60/35/5 and I should then recalculate the mortality rate using the revised weightings.
Helen
Thanks Helen for the example. I'm still confused why these two are separate risks _the point for both your examples is that they're calculating a single age 50 mortality rate for a range of employee categories!
(the only difference is that in your second example (which i've quoted) there is sufficient data to create homogeneous groups but ultimately they still weight a single mortality rate to apply to a wide heterogeneous group based on these smaller homogeneous groups.)
The Core Reading (chapter 18 page 9) also lists:
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future trends not being reflected sufficiently in past data
- past data may not be sufficiently up to date
What is the difference between these two risks (and if there isn't one, would they be awarded separate marks in an exam just because the core reading lists them separately)?
In the world of motor insurance (rather than benefits), would the following be examples of the different risks of using historical claims data:
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past abnormal events = covid lockdown which temporarily reduced no. of claims due to reduced car use;
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significant random fluctuations = if there was an unusually high/low number of payouts in a past period, for no apparent reason;
- future trends not being reflected sufficiently in past data = in a developing country, past data won't allow for a future increase of more expensive cars (&therefore higher sum assureds&cost of repairs);
- past data may not be sufficiently up to date = past claim sizes don't reflect recent inflationary increases (affecting cost of car repairs, medical injuries etc)
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changes in the way past data recorded - If past claims data doesn't
Change in balance of any homogeneous groups underlying the data
other changes- increased use of public transport/lower speed limits so expect reduced accidents