Question: For how many years was the Mexican Billionaire in 2015 ranking considered to be the richest person in the world by the Forbes business magazine ?

text: The World's Billionaires
Annual rankings -- 2015
Main article : The World 's Billionaires 2015 In the 29th annual Forbes list of global billionaires , a record 1,826 billionaires were named with an aggregated net worth of $ 7.1 trillion compared to $ 6.4 trillion in the previous year . 46 of the billionaires in this list were under the age of 40 . A record number of 290 people joined the list for the first time , of whom 25 percent hailed from China , which produced a world-leading 71 newcomers . The United States came in second , with 57 ; followed by India , with 28 ; and Germany , with 23 . [ 24 ] The United States had the largest number of billionaires with 526 . Russia went down to 88 from 111 in 2014 . Russia was placed behind China , Germany and India by the number of billionaires . Self-made billionaires made up the largest number of people on the list with 1,191 positions ( over 65 percent ) , while just 230 ( under 13 percent ) had wealth through inheritance . The number of billionaires who inherited a portion but were still working to increase their fortunes is 405 . [ 25 ] Bill Gates was named the richest man in the world by Forbes ' annual list of the world 's billionaires . This was the 16th time that the founder of Microsoft claimed the top spot . Carlos Slim came in second for the second consecutive time . Warren Buffett of Berkshire Hathaway placed third , while Amancio Ortega of Spain , slipped down a position from the previous year to number four . Larry Ellison , the founder of Oracle , rounded off the top five . Christy Walton was the highest-ranking female at number eight . America 's Evan Spiegel , co-founder of photo messaging app Snapchat , became the youngest billionaire this year at age 24 . At age 99 , David Rockefeller maintained his position as the oldest billionaire included in the list . [ 26 ] Mark Zuckerberg , the founder of Facebook , rose to number 16 with $ 33.4 billion . Iceland had a billionaire , Thor Bjorgolfsson , in the list after a gap of five years . Guatemala had a billionaire , Mario Lopez Estrada , for the first time in its history . [ 27 ]
The World's Billionaires is an annual ranking by documented net worth of the wealthiest billionaires in the world, compiled and published in March annually by the American business magazine Forbes. The list was first published in March 1987. The total net worth of each individual on the list is estimated and is cited in United States dollars, based on their documented assets and accounting for debt. Royalty and dictators whose wealth comes from their positions are excluded from these lists. This ranking is an index of the wealthiest documented individuals, excluding and ranking against those with wealth that is not able to be completely ascertained. In 2018, there was a record of 2,208 people on the list, that included 259 newcomers mostly from China and the U.S.; there were 63 people under 40 and it had a record number of 256 women. The average net worth of the list came in at US$4.1 billion, up US$350 million from 2017. Added together, the total net worth for 2018's billionaires was US$9.1 trillion, up from US$7.67 trillion in 2017. As of 2018[update], Microsoft founder Bill Gates had topped the list 18 of the past 24 years, while Amazon founder Jeff Bezos is ranked at the top for the first time and he became the first centibillionaire included in the ranking. In 2017, Mark Zuckerberg was the only person in the top 10 billionaires list who is under the age of 50, and the only one in the top 20 billionaires list who is under the age of 40. In 2017, 500 of the richest people in the world became richer by $1 trillion, according to a report by Bloomberg News. According to a 2017 Oxfam report, the top eight billionaires own as much combined wealth as the poorest half of the human race.
No Name Net worth ( USD ) Age Nationality Source ( s ) of wealth
1 Bill Gates $ 79.2 billion 59 United States Microsoft
2 Carlos Slim $ 77.1 billion 75 Mexico América Móvil , Grupo Carso
3 Warren Buffett $ 72.7 billion 84 United States Berkshire Hathaway
4 Amancio Ortega $ 64.5 billion 78 Spain Inditex
5 Larry Ellison $ 54.3 billion 70 United States Oracle Corporation
6 Charles Koch $ 42.9 billion 79 United States Koch Industries
6 David Koch $ 42.9 billion 74 United States Koch Industries
8 Christy Walton $ 41.7 billion 66 United States Walmart
9 Jim Walton $ 40.6 billion 66 United States Walmart
10 Liliane Bettencourt $ 40.1 billion 92 France L'Oreal