The Russian billionaires hit hard by oil's plunge
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.
Read MoreTheBig Vlad? Is Moscow taking on McDonald's?
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.
"(However), the Russian billionaire whose fortune took the biggest hit in 2014 was Leonid Mikhelson, chairman and CEO of gas firm Novatek, who lost U$7 billion – over 40 percent of his net worth," according to the census, Schneider said.
Other members of the exclusive billionaire's club who have seen their fortunes slashed are Vladimir Lisin, chairman and largest shareholder of Novolipetsk Steel; Andrey Melnichenko, who has interests in mining and fertilizer and Sergey Galitsky, founder and owner of food retailer Magnit, although the losses they have seen were not documented by Schneider.
Read MoreRussia needs oil at$102 to survive: Strategist
In addition, German Khan, executive director at oil firm TNK and Mikhail Prokhorov, owner of both the investment fund ONEXIM Group and the National Basketball Association's Brooklyn Nets, have also seen their fortunes reduced.
Although Russia's billionaires may provide the most prominent examples of fortunes diminished by plunging oil prices, the trend is not entirely a Russian phenomenon, Wealth-X's analyst said.
In December 2014, Harold Hamm, chief executive of Oklahoma-based Continental Resources, claimed (during divorce proceedings) that the slide in oil prices had knocked $10 billion off his net worth.
Read MoreHow sanctions arehurting Russia's energy sector
Oil prices have rebounded of late to currently trade around $64 a barrel for benchmark Brent crude and around $59 for U.S. crude. But should prices stay low for a while, Russian billionaires could face more losses, Schneider warned.
"A prolonged period of low oil prices will likely lead to a continued contraction of the country's economy and low or negative growth in industries beyond the oil patch such as banking, credit cards and others. For those billionaires remaining in Russia, this may well translate to rougher waters (and more potential losses) ahead."
- By CNBC's Holly Ellyatt, follow her on Twitter @HollyEllyatt. Follow us on Twitter: @CNBCWorld