Inequality Among Citizens in the World
You might think that it would be easy to combine the inequality among individuals within nations and inequality between nations and estimate the extent of global inequality across all citizens of the world. This is, unfortunately, not the case.
First, we lack the necessary data. While the data on GDP per capita that go into the construction of between-country inequalities can be reasonably well estimated from the early nineteenth century (and, as we have seen, even for the ancient societies, like the Roman Empire), the data on within-national distributions are much more recent. The household surveys we need to calculate income differences among individuals within each single ...