Measured expected lifespan and actual expected lifespan

Imagine a country. The fertility rate is far below the replacement rate. The population is aging rapidly. To ease labor shortage, it imports large number of foreign labors. Suppose all the newcomers have a lifespan of exactly seventy years. The native population all have exact lifespan of ninety years. Since most of the newcomers are still far below seventy years old, their death number is small and hence has little weight in the measurement of expected lifespan. As a result, the measured expected lifespan is very close to ninety years old. However, for people born today, the percentage born from newcomers is much higher. So the actually expected lifespan will be much lower than ninety years old for today’s new born, although the official expected lifespan is ninety.

In a word, when there is a significant demographic transformation, the official expected lifespan doesn’t accurately describe the true expected lifespan of today’s new born. There is a similar problem for the measurement of total fertility rate during significant demographic transition.

Many countries are in significant demographic transitions now. The general populations, the policymakers and the researchers seem to be oblivious of this important problem.

See also:

On the measurement of total fertility rate: With understanding on the impacts of population policies

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