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Lee Carter model 'b' parameter

E

Edward Smith

Member
Why is the effect of b less apparent at older ages? Intuitively I would have thought time would have a greater effect on death at older age
 
Hi Edward

First thing to note is that the notes are talking about empirical observation here rather than model effects, which I think is what you mean, but I want to be clear for anyone else reading this thread.

The effect that is described here is that life expectancy has been increasing rapidly over time, and mortality at "normal" ages (ie ages that most people attain) is reducing. If this was true for all ages, then we would expect the distribution of human lifetimes to get longer in the tail as these effects compound over a lifetime. However what we see is a "bunching up" of mortality at extremely old ages, which suggests a natural limit on how long humans can live.

This is effectively the same as saying that the effect of b is less apparent at older ages, ie mortality remains extremely high in the very old.

Dave
 
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