https://www.destatis.de/Europa/EN/Topic/Economy-Finance/Debt.html
https://www.brookings.edu/articles/the-difference-in-how-the-wealthy-make-money-and-pay-taxes/
https://www.econstor.eu/bitstream/10419/283282/1/1877510009.pdf
https://www.esri.ie/system/files/publications/WP677_0.pdf