Can Heterogeneity of Populations Explain Differences in Mortality?
We investigate whether heterogeneity can explain the differences in mortality between
the United States and a more homogeneous country, i.e. Japan. The background of the analysis
is the growing gap between life-expectancy in the United States and the world record leader
since the 1980s. This development is mirrored in the decelerated improvements made against
mortality during the last 25 years — especially for women.
Our hypothesis is that it
is possible to have survival improvements at a steady pace across all population subgroups.
The proportion of the population subgroups which perform relatively well decreased over
time whereas poor performing subgroups became more important. The consequence of this
compositional change since the 1980s would be the observed leveling off in survival improvements
on the population level.
Since official mortality estimates in the US are of poor quality,
we estimate mortality rates via the extinct cohort method using Medicare enrollment data
from the Social Security Administration due to their higher quality.
If our hypothesis
was true, we should see little differences in the development of mortality rates between
the best performing subgroups in the United States and Japan. We compared mortality rates
between Japanese women and white women in the US from states who (a) either had the highest
life expectancy or (b) the highest median household income or (c) the largest gross state
product per head. Regardless of the choice of indicator, mortality rates leveled-off
in the United States for those best performance subgroups as for the whole population.
preliminary conclusion is therefore that compositional changes (heterogeneity) in
the US population can not explain the widening gap between US life expectancy and best practice