It seems like this study considers income from work, but not income from capital.

In Sweden, the marginal tax rate for work has hovered around 70% for the past decades. Taxes on capital around 30%.

https://www.ekonomifakta.se/Fakta/Skatter/Skatt-pa-arbete/ma...

Anyone who isn't stupid (and study considers IQ, after all) would move their income from work to capital.

There are several ways, for example starting a company. Even stuff that's basically a job, like high-paid people finance and law, would have a setup that have them earn their primarily as income from capital.

Unless this study has considered this, I'd say that they are missing a lot of people at the far end of the income spectrum.

https://www.scb.se/hitta-statistik/artiklar/2018/stor-del-av...

https://www.scb.se/hitta-statistik/artiklar/2022/svenskarnas...