The sharp fall in global oil prices has had a deep impact not only on the global economy but on the fortunes of Russian billionaires, many of whom got rich on the back of the commodity.
According to the 2014 Wealth-X and UBS Billionaire Census, the net worth of many of the 114 Russian billionaires in the index has been sorely affected by lower oil revenues and the value of their holdings in petroleum-related businesses.
International sanctions imposed on Russia for its annexation of Crimea and role in the conflict in east Ukraine, the drop in the Russian ruble and the ensuing rampant inflation have not helped matters either, and have all contributed to Russia's economy sliding towards recession this year.
Among the billionaires most affected by this confluence of factors is Alisher Usmanov, the majority shareholder of mining firm Metalloinvest and at one time the wealthiest man in Russia, according to Max Schneider, director of research of Americas at Wealth-X who delved into the Census' data.
"Usmanov lost $4.5 billion between March 2014 and December 2014, which represented nearly 25 percent of his fortune," Schneider said in a research note from Wealth X this week.
Other "victims" of the fall in commodity prices included Mikhail Fridman, chairman of investment firm Alfa Group, who lost $2.7 billion – approximately 18 percent of his fortune – during the same period.