  The influence of per capita income on life expectancy is well documented,
mostly through studies of multinational samples. However, one expects fairly
weak correlations at both ends of the life span, that is to say in early
infancy and in age groups of elderly from 85 to 100 years. The reason is that
at both ends mortality is largely controled by biological factors rather than
by socio-economic conditions. In order to test this conjecture, we explore the
influence of income on age groups, separately in France, the United States and
South Korea. More precisely in each country we compare income and mortality
data in as many regional subunits as possible. One noteworthy constatation is
that, contrary to a common view, personal income is only weakly correlated with
infant mortality (i.e. mortality under the age of one year). More broadly, we
propose as a conjecture that the common pattern revealed by the analysis of the
three countries is also valid in other developed countries.
