A day after Jeff Bezos proudly announced that he intends to take a trip to space this summer, ProPublica has shed some light on how he and other U.S. billionaires have managed to amass such a ridiculous amount of wealth. The site obtained a huge Internal Revenue Service data trove that holds the tax returns from thousands of the richest people in America. It reportedly shows the Amazon CEO paid zero federal income taxes in 2007 and 2011. Tesla chief Elon Musk reportedly did the same in 2018, and George Soros reportedly managed to pay zero federal income tax for three years running. The site calculated what it called the “true tax rate” of U.S. billionaires by comparing how much they paid in taxes with how much their estimated wealth grew in the same period. Warren Buffett’s rate stood at 0.1 percent, Bezos’ reached 0.98 percent, and Michael Bloomberg’s was given as 1.3 percent. Buffett’s figure is the lowest, with the site estimating he paid less than 10 cents in tax for every $100 boost to his wealth.