Some entrepreneurs dream up businesses that make them into billionaires virtually overnight while others work for decades to join the three comma club. Once they get there, some choose to do some questionable things with their money – but this article is concerned solely with how long it took some of the richest people in the world to get there. According to an analysis of the Forbes ' 2020 Billionaires List by British sports betting firm OLBG, it takes the average billionaire 21 years to make their first billion. Some, like Facebook CEO Mark Zuckerberg, do it much faster while others, such as Zara billionaire Amancio Ortega, take a bit longer to amass their massive fortunes. It’s worth noting at this point that the ranking only includes self-made billionaires, so those who inherited their fortunes, like the Waltons of Wal-Mart, have been excluded. OLBG determined how long each individual took to become a billionaire by subtracting the year they founded their primary business from the year Forbes declared them a billionaire. Jeff Bezos and 10 other US billionaires who got richer during the pandemic No one on the 2020 Billionaires List was inducted into the three-comma club faster than eBay founder Pierre Omidyar, however, who made a billion dollars in just three years after founding the online auction house. 11. Carlos Slim, the richest man in Mexico, took 30 years to become a billionaire Current net worth: US$53.2 billion (attributed to Slim and his family) Source of wealth: Telecommunications giant America Movil Slim, 80, and several of his family members, control Latin America's largest telecommunications company. He has also invested in construction, consumer goods and real-estate firms in Mexico, in addition to holding a stake in The New York Times, according to Forbes . Who are the 15 richest women in the US? 10. It took Spanish fashion mogul Amancio Ortega 26 years to join the three-comma club Current net worth: US$63.3 billion Source of wealth: Zara parent Inditex The 84-year-old Spaniard began his career in textile manufacturing but went on to co-found fast-fashion retailer Zara with his late wife Rosalia Mera in 1975. 9. Warren Buffett's conservative investing philosophy meant it took him 23 years to become a billionaire Current net worth: US$72.5 billion Source of wealth: Berkshire Hathaway conglomerate Investor Warren Buffett has made his fortune running conglomerate Berkshire Hathaway, which owns fast food staple Dairy Queen and insurer Geico. Why do millionaires and billionaires pay so little for their houses? 8. Fashion CEO Bernard Arnault took 13 years to become a billionaire Current net worth: US$112.1 billion Source of wealth: Luxury brand conglomerate LVMH French businessman Bernard Arnault, 71, is the richest person in the fashion industry. However, the pandemic temporarily reversed their fortunes, sending both LVMH's share price and Arnault's net worth into free fall. 5 Chinese tycoons who lost billions thanks to Covid-19 7 and 6. It took Microsoft's Steve Ballmer and Bill Gates 12 years to become billionaires Current net worths: US$113.6 billion (Gates), US$72.1 billion (Ballmer) Source of wealth: Microsoft Bill Gates, 64, founded software giant Microsoft with his high school friend Paul Allen in 1975. The company made Gates a billionaire in 1986, the year after it went public, according to CNBC. Jeff Bezos and 10 other US billionaires who got richer during the pandemic Ballmer became one of Microsoft's first employees after dropping out of Stanford Business School in 1980, according to Forbes . Ballmer's Microsoft stake also made him a billionaire. He spent 14 years as Microsoft's CEO after Gates stepped down from the top post, and now owns the Los Angeles Clippers professional basketball team. 5. Larry Ellison became a billionaire nine years after founding Oracle Current net worth: US$72.4 billion Source of wealth: Oracle Larry Ellison, now 75, co-founded software firm Oracle to produce customer relationship management databases. A two-time college dropout, Ellison is now best known as an international playboy and tech titan. 4 and 3. It took Google co-founders Sergey Brin and Larry Page six years to become billionaires Current net worths: US$67.5 billion (Brin), US$69.3 billion (Page) Source of wealth: Google parent Alphabet Larry Page and Sergey Brin co-founded Google in 1998 while working towards their PhDs at Stanford, according to Forbes . The pair went on to spend decades atop Google parent Alphabet – with Page as CEO and Brin as president – before stepping down in December 2019. 10 things you didn’t know about Google co-founder Sergey Brin 2. Jeff Bezos is richer than anyone else in history – and it only took five years to become a billionaire Current net worth: US$183.1 billion Source of wealth: Amazon Jeff Bezos, 56, left his job at a New York City hedge fund to sell books on the internet in 1994. That company, called Amazon, became the world's largest retailer and made its CEO the world's richest man in the process. What does Facebook CEO Mark Zuckerberg do every day? Current net worth: US$87.9 billion Source of wealth: Facebook Mark Zuckerberg, 35, founded the social network in his dorm room at Harvard. Zuckerberg's 15 per cent stake in the company makes him the seventh-richest person on the planet according to Forbes , but the billionaire has said that he and wife Dr Priscilla Chan plan to give most of their wealth away. Want more stories like this? Sign up here . Follow STYLE on Facebook , Instagram , YouTube and Twitter . This article originally appeared on Business Insider.