Mokhzani Mahathir falls out of the billionaire ranks, a victim of the global oil-price collapse that cost him $500 million. Son of former Prime Minister Mahathir started as an engineer for Shell and later built oil-and-gas equipment-fabricating company Kencana Petroleum. It merged with an offshore oil-and-gas services provider and his stake in the new company, SapuraKencana Petroleum, makes up the bulk of his fortune. A car racing enthusiast, he hosts Malaysia's Formula One race, to be held on March 29 this year.