Maddison defines the frontier as the group of four “settler economies”: Australia, Canada, New Zealand, and the United States. For two centuries, these economies have enjoyed average living standards at least 2.5 times those of other regions.

But this comparison is based on regional averages: for example, the GDP per capita of East Asia relative to that of the frontier. It also relies on national accounts data, which are a poor proxy of individual welfare.

So I wanted to find out what happens when we move beyond regional averages and look at the actual distribution of incomes, using survey data. Does the 90% figure still hold?

It does!

The chart below shows the global distribution of household income in 2025. Each unit of mass represents people. Colors distinguish regions, while the width of each distribution captures the dispersion of income within a region.

The mean income of the four frontier economies is $94 per person per day. Forty per cent of this amounts to roughly $37.And 84% of the world’s population lives below that threshold. Not quite 90%, but remarkably close.

Did the same pattern hold over the past 200 years? We cannot know for sure: comparable household surveys do not extend that far back.

Looking ahead, I expect AI to widen these disparities further. Differences in capabilities, infrastructure, and access to AI risk amplifying the gap between economies at the frontier and those far behind.The next great divergence may be upon us already, even as we’re still dealing with the consequences of the previous one.