Second, such stability or reduction in the inequality of the percentage
shares was accompanied by significant rises in real income per ca pita.
The countries now classified as developed have enjoyed rising per
ca pita incomes except during catastrophic periods such as years of
active world conflict. Hence, if the shares of groups classified by their
annual income position can be viewed as approximations to shares of
groups classified by their secular income levels, a constant percentage
share of a given group means that its per ca pita real income is rising
at the same rate as the average for all units in the country; and a reduction in inequality of the shares means that the per ca pita income
of the lower-income groups is rising at a more rapid rate than the per
ca pita income of the upper-income groups.