(probably…maybe? that seems like something that might need more research to quantify, and probably has easily skewable results in either direction)

The income distribution would get you closer. The typical way to measure it would be amount earned minus amount saved, right?

Besides being fewer, richer people are able to save a bigger percentage of their earnings. That puts the middle class in kind of a consumption sweet spot - which is why the big businesses mostly target them.

If you want to measure less tangible things like carbon emissions or social opportunities it gets much more complicated, although I have no reason to think the overall story would change.

but us living in the ‘core’ are the 1% of the world

I should point out the international picture is nuanced in a similar way. There's middle income countries, there's very rich people in poor countries, and there's countries like Dubai that kind of defy categorisation. The basic picture that the West is rich holds, but not that it's all the wealth, and developing economies are quickly catching up because it's just easier for them to grow. (Developed countries also account for a bit more than 10% of world population)