Revealed: the 10 richest people on the planet
And where is the billionaire's capital of the world?
The study found that Moscow has taken the title of the billionaire's capital of the world - with 76 billionaires. In second place is New York, then Hong Kong, Beijing and London.
Yet the vast majority of the world's richest billionaires shun the bright lights of these cities. So who are the ten richest people on the planet, where are they, and how did they make their money?
1. Carlos Slim Helu and his familyThe Mexico City telecoms mogul is worth an estimated $66 billion - making him the richest man in the world.
His money originally came from his telecoms business, but he has since built an empire spanning everything from mining and real estate to newspapers and football clubs around the world.
2. Warren BuffettThe man known as the Sage of Omaha is said to be worth $58 billion - made from his investing business - which has also made countless other millionaires.
He is notable for his incredible level of philanthropy, and the fact he called on the US government to tax the rich.
3. Amancio OrtegaThe retail giant from La Coruna is worth $55 billion. His global fashion company Inditex lay behind the fortune.
He stepped down in 2011, and has since made an extraordinary range of personal investments - in everything from a skyscraper in Madrid to a stake in a horse jumping circuit and a hotel.
4. Bill GatesMicrosoft made Bill Gates an incredibly wealthy billionaire, who is said to be worth $54 billion. However, nowadays he is best known for his charity work. His foundation has become the largest transparent private charitable foundation in the world, giving billions of dollars to support international healthcare projects.
5. Bernard ArnaultThe French business magnate and art collector is worth an estimated $51 billion. He is the director of luxury firm LVHM, and has become a major patron of the arts in Paris.
6. Larry EllisonThe co-founder of Oracle is worth an estimated $43 billion, largely through a large stake in the company. However, he hasn't been shy of investing his fortune in a variety of things - most recently buying himself an island and an airline in Hawaii.
7. Li Ka-shingThe Hong Kong business man is worth a reported $32 billion and is said to be the richest man in Asia. His companies make up 15% of the market cap of the Hong Kong stock exchange, and range from plastic manufacturing to real estate, retail and technology.
8= Charles and David KochThe first men of inherited wealth in the list are worth $31 billion each. They inherited their father's business - although in their lifetimes they have increased the size of the business by thousands of times. The brothers are involved in businesses ranging from chemicals to oil refinery and toilet roll. They also give hundreds of millions of dollars to charity.
10 Liliane BettencourtThe daughter of the founder of L'Oréal is said to be worth $30 billion. She continues to own a large chunk of the stock of the company from her home in Paris, and now has a stake in Nestlé too.
She donates a great deal of money to charity, and is also rumoured to spend a fortune supporting conservative politicians in France.