> Poor countries generally have much greater inequality than wealthy countries, with the result that elites in poor countries (say, top 1%, 5%, or 10% by either net worth or income) are often wealthier than elites in richer countries.

This is false, and massively so. Look here: https://ceoworld.biz/2020/02/07/how-much-the-top-1-of-worlds...

The relationship between Gini and GDP is complex and the correlations are small. The top 1% of poor countries like Haiti or Bangladesh are not richer than the top 1% of the US, they are much poorer, because even if the lorenz curve is such that 1% of the population get 40% of the income in one place and 30% in another -- which is a huge change -- it does not change the fact that one of these has a GDP of $800 per capita, and the other of $70,0000. This is really just math and an understanding of the definitions, plus a rough understanding of the possible differences in Lorenz curves (hint: in poor countries, there just isn't that much of a surplus for the wealthy to accumulate and Lorenz curves don't vary that much).

> Generally, the answer in cases like this is "almost".

Also false. Gross Domestic Output is usually 150% of Gross Domestic product, and then market income varies much more because NIPA (National Income Product Accounts) throws away spending on purchase and sale of assets, nor does it care about moving money around, but it tries to focus purely on net addition of domestic production, with appropriate netting for intermediate inputs. Here are the definitions - https://www.bea.gov/resources/methodologies/nipa-handbook. National income and product accounts can be a little confusing, but it's not too hard and you do need to know what GDP is before getting into discussions about it.

Here is a brief summary: GDP is production of final goods services in a region. If an island that produces fish has 1000 billionaires move to it. Then the GDP of the island only increases by the number of extra fish that are produced to feed the billionaires when they live there. Once you understand this point, and stop thinking that the billionaires are somehow adding to the island's GDP with their billions, then you will have an idea of what GDP actually is, and then you will have a better intuition for the methods of measuring a billionaire's contribution to GDP. But it does take some study because GDP, as an economic concept, tries to measure actual production of final output, and is not a measure of market income at all.

> Your explanation leaves out what she does with the money after she gets it.

Yes, because I do not double count. You can measure final output by looking at what everyone earns from producing goods with appropriate netting, or you can measure final output by looking at what people spend on the purchase of other's production, again with appropriate netting, but it is really double counting to do both at the same time. We are talking about how much Taylor Swift produces. Her purchase of other people's production doesn't get added to her own production. That is their production and they deserve the credit for doing it, whether that is equipment for recording studios, marketing people, construction workers maintaining venues, all those others involved in the music business who also contribute to GDP, not just Taylor Swift. And if she retired, they would work for someone else, continuing to produce. Similarly, when Taylor buys someone else's production, that does not add to her own production, it is the production of whoever produced that good. If Taylor likes fine cuisine, then cooks are the ones adding to GDP when she buys their food. GDP is a measure of production in an economy. We can change this and look at GDI, and try to measure income -- what people spend on production. In that case, we would only look at Taylor's spending, and we wouldn't look at her earnings at all. But what you want to avoid is doing both.