… is from page 14 of Julian Simon’s Introduction to his brilliant 1995 edited volume, The State of Humanity (original emphasis):
Data on the absolute gap between yearly incomes of the rich and poor countries are beside the point; widening is inevitable if all get rich at the same proportional rate, and the absolute gap can increase even if the poor improve their incomes at a faster proportional rate than the rich. Here one should notice that increased life expectancy among the poor relative to the rich reduces the gap in lifetime income, which is a more meaningful measure than yearly income.
Of course, the same holds true when speaking of the incomes of rich and poor individuals or families.
