Look at Russia, where one hundred billionaires control fortunes worth an astonishing 20 percent of national GDP. Russia has nearly as many billionaires as China but they control twice as much total wealth in an economy one-fourth the size. Just as striking, Russia is missing not only a middle class but also a millionaire class; according to Boston Consulting Group, China ranks third in the world for number of millionaires, while Russia is not even in the top 15 for millionaires.
(It is, of course, worth adding that as GDP is a measure of flows and worth is a measure of stocks, the two numbers are not directly comparable. The inference that "oligarchs own a fifth of Russia" would be incorrect)