Now. back to an original question - why does NATS not take REAL life expectancies into account ? That shouldn't be too hard to work out.
Because there is a big difference between age of death data and life expectancy. The regulator will allow Actuaries to use industry life expectancy figures if they can justify them but it's hard enough coming up with a life expectancy figure for the population as a whole let alone a very small subset of the population. For actuaries there is safety in numbers, by using the same figure as every one else they are following good practice and less liable than if they branched out and used something different.