The expectation of life (cont.)
Exercise 2
Answer the following questions using the graph. Before checking your answers write a few words of explanation and interpretation in the answer box.
What happens to e0 if you double risks of death at all ages?
Life expectancy drops to 66.2. You might consider this quite a small drop seeing that risks of dying have been doubled at all ages.
What would be the effects of halving or doubling only childhood mortality (first 2 factors)?
Halving childhood mortality risks raises LE to 74.6. Doubling risks at those ages changes LE to 73.6 These are quite small effects because childhood mortality is already very low (5q0 only 8 per thou).
What would be the effects of halving or doubling only ages 55+ (last factor)?
Halving older age mortality increases LE to 78.1, doubling risks reduces LE to 71. These are more substantial effects than for childhood because they are affecting ages where mortality risk is already quite high, therefore a factor of 2 changes mortality at these ages quite considerably.
In Britain in the distant past, and in some developing countries until quite recently, expectations of life of 35 years were not unknown. Adjust the life table, by using appropriate multiplication factors, to achieve an e0 of 35 years. What do you learn from this process?
Factors of 37, 28, 17, 7, 1.5 or 30, 49, 18, 7, 1.5 produce a LE of 35 years. Other combinations would be possible and the exact values are not important. What is important is the interpretation that it is impossible to reduce LE to such very low values without a very high levels of young age mortality. Under these scenarios 5q0 is well over 200 per thou.
Under this high mortality scenario what would be the effect of halving childhood mortality (first 2 factors)? Compare with gains from halving mortality in the initial low mortality situation.
Answer: Halving the very high risks brings LE to approximately 42 – adding about 7 years. This is a considerable amount because halving something very large makes a big difference.
The message is that in high mortality situations, such as in some developing countries, life expectancy is quite sensitive to reducing child mortality, because that is where a large part of the problem resides. This is the reason why many developing countries have shown large improvements in LE as a result of interventions aimed particularly at children. Adult LE may not be changing to the same degree. The situation is reversed in low mortality situations - because child mortality is already low changes to LE will be more sensitive to mortality patterns at adult ages.
The following page has a further exercise using the interactive graph.