Many billionaires are taxed differently or not at all on their wealth given that much of their gains are unrealized—meaning they haven't sold any stock or equity, and thus, haven't had to pay taxes yet. As well, while some billionaires hold several billion dollars in cash, many also have investments in private assets, such as private companies, real estate, or other public companies.

 But since much of the top billionaires' wealth is wrapped up in public equity, their net worth can fluctuate a lot from year-to-year. For example, Elon Musk, founder and CEO of Tesla and the richest person in the world as of Jan. 19, 2022, saw his net worth surge in 2021 thanks to the increase in Tesla shares (where he owns 23% of the company)—with shares of Tesla rising over 32% in 2021.

 Below are the 10 individuals currently considered the wealthiest at the time.

 Elon Musk

•  Age: 50
•  Residence: Texas
•  Co-founder and CEO: Tesla (TSLA)
•  Net Worth: $269 billion
•  Tesla Ownership Stake: 18% ($186 billion)
•  Other Assets: Space Exploration Technologies ($40.3 billion private assets), $4 billion in cash.

 In 2004, Musk became a major funder of Tesla Motors (now Tesla), which led to him being retroactively declared a co-founder and his current position as CEO of the electric vehicle company. In addition to its line of electric automobiles—which include sedans, sport utility vehicles (SUVs), and the "Cybertruck" announced in 2019—Tesla also produces energy storage devices, automobile accessories, merchandise, and, through its acquisition of SolarCity in 2016, solar power systems.

 In 2020, Tesla’s stock price experienced an astronomical serge—rising over 740%, helping push Musk to the top spot among billionaires. In December 2020, Tesla joined the S&P 500 that same month, the largest company added thus far.

 In 2016, Musk founded two more companies, Neuralink and The Boring Company, with him serving as the CEO of the former. The Boring Company, meanwhile, develops boring machines for drilling tunnels for underground public transportation systems, which would mitigate traffic congestion in major cities. It also (briefly) sold a handheld flamethrower.

 On Oct. 25, 2021, shares of Tesla spiked 12.7% and surpassed a $1 trillion market cap after car rental company Hertz announced its plan to order 100,000 of the automaker's electric vehicles. Thanks to the surge in Tesla shares and a deal with investors in October 2021 that boosted the valuation of SpaceX, Musk's lead as the richest person in the world continues to grow. As of Jan. 19, 2021, Musk's net worth had grown by $72 billion over the last year.

 Jeff Bezos

•  Age: 58
•  Residence: Washington
•  Founder and Executive Chair: Amazon (AMZN)
•  Net Worth: $187 billion
•  Amazon Ownership Stake: 10% ($162 billion)
•  Other Assets: Blue Origin ($9.15 billion private assets), The Washington Post ($250 million private assets), and $16.1 billion in cash.

 In 1994, Jeff Bezos founded Amazon.com in a garage in Seattle, shortly after he resigned from the hedge fund giant D.E. Shaw  He had originally pitched the idea of an online bookstore to his former boss David E, who wasn’t interested.

 Though Amazon.com originally started out selling books, it has since morphed into a one-stop shop for everything under the sun and is arguably the world’s largest retailer. At any rate, it is hard to dispute its self-description as the Earth's most customer-centric company. Its pattern of constant diversification is evident in some of its unexpected expansions, which include acquiring Whole Foods in 2017 and launching its own branded over-the-counter drugs.

 In 2020, Amazon’s share price skyrocketed on the heightened demand for online shopping as lockdowns forced consumers to stay home. Shares were up 76% in 2020. On July 2021, Bezos stepped down as CEO of the e-commerce giant and transitioned to his new role as its executive chair.

 Bezos originally took Amazon public in 1997 and went on to become the first man since Bill Gates in 1999 to achieve a net worth of more than $100 billion. Bezos’s other projects include aerospace company Blue Origin, The Washington Post (which he purchased in 2013), and the 10,000-year clock—also known as the Long Now.

 On July 2021, Bezos, his brother Mark, aviation pioneer Wally Funk, and Dutch student Oliver Daemon completed Blue Origin's first successful crewed flight, reaching an altitude of just above 62 miles before landing safely.

 Bernard Arnault

•  Age: 72
•  Residence: Paris, France
•  CEO and Chair: LVMH 
•  Net Worth: $164 billion
•  Christian Dior Ownership Stake: 97.5% ($137 billion total)
•  Other Assets: M E O L I S & Company equity ($24.6 billion public assets), Hermès equity (undisclosed stake), and $11.2 billion in cash.

  French national Bernard Arnault is the chair and CEO of LVMH, the world’s largest luxury goods company. This business owns some of the biggest brands on Earth, including Louis Vuitton, Hennessy, Marc Jacobs, and Sephora.

 The majority of his wealth, however, actually comes from his massive stake in Christian Dior SE, the holding company that controls 41.2% of LVMH. His shares in Christian Dior SE, plus an additional 6.2% in LVMH, are held through his family-owned holding company, Group Familial Arnault.

 An engineer by training, Arnault's business chops became apparent while working for his father’s construction firm, which he would take control of in 1971. He later converted to a real estate company named F E R I N E L Inc.

 Arnault remained chair for another six years until he acquired and reorganized luxury goods maker Ag aches in 1984, eventually selling all of its holdings other than Christian Dior and Le B o n March e. He was invited to invest in LVMH in 1987 and became the majority shareholder, chair of the board, and CEO of the company two years later.

 Bill Gates

•  Age: 66
•  Residence: Washington
•  Co-founder: Microsoft Corp. (MSFT)
•  Net Worth: $133 billion
•  Microsoft Ownership Stake: 1.3% ($31.9 billion)
•  Other Assets: Cascade Investment LLC ($60 billion public and private assets), $56.5 billion in cash.

 While attending Harvard University in 1975, Bill Gates went to work alongside his childhood friend Paul Allen to develop new software for the original microcomputers. Following this project’s success, Gates dropped out of Harvard during his junior year and went on to found Microsoft with Allen.

 In addition to being the largest software company in the world, Microsoft also produces its line of personal computers, publishes books through Microsoft Press, provides email services through its Exchange server, and sells video game systems and associated peripheral devices. Originally Microsoft's chief software architect, Gates later transitioned to the role of chair in 2008. He had joined Berkshire Hathaway’s board in 2004. He stepped down from both boards on March 13, 2020.

 Bill Gates has much of his net worth wrapped up in Cascade Investment LLC. Cascade is a privately-held investment vehicle that owns a variety of stocks—such as Canadian National Railway (CNR), Deere (DE), and Republic Services (RSG)—as well as private investments in real estate and energy.

 In 2000, Gates' two philanthropic organizations—the William H. Gates Foundation and the Gates Learning Foundation—were merged to create the Bill & Melinda Gates Foundation, of which he and his ex-wife, Melinda Gates, are co-chairs. Through the foundation, he has spent billions to fight polio and malaria. Additionally, he pledged $50 million in 2014 to help fight Ebola. As of 2021, the foundation has spent more than $1.9 billion to combat the COVID-19 pandemic.

 In 2010, alongside Warren Buffett, Bill Gates launched the Giving Pledge, a campaign encouraging rich individuals to commit to donating the majority of their wealth to philanthropic causes. Of note, Bill and Melinda Gates announced plans to divorce in 2021—it remains to be seen how Bill Gates' net worth will be affected post-divorce.

 Larry Page

•  Age: 48
•  Residence: California
•  Co-founder and Board Member: Alphabet (G O O G)
•  Net Worth: $124 billion
•  Alphabet Ownership Stake: 6% ($107 billion total)
•  Other Assets: $14.4 billion in cash.

 Like several tech billionaires on this list, Larry Page's claim to fame got its start in a college dorm room. While attending Stanford University in 1995, Page and his friend Sergey Brin came up with the idea of improving data extraction capabilities while accessing the Internet. The duo devised a new type of search engine technology they dubbed back rub, named after its ability to analyze "backing links." From there, Page and Br in went on to found Google in 1998, with the former serving as CEO of the company until he stepped down in 2001.

 Google is one of the largest Internet search engines on the planet, accounting for more than 92% of global online search requests. In 2006, Google (the company) expanded by purchasing YouTube, the biggest platform for user-submitted videos. Then, 2008 saw the release of the first mobile phone utilizing the Android operating system, which was originally developed by Android Inc. before Google acquired the company in 2005. Today, Google is a subsidiary of Alphabet, a holding company for which Page served as CEO from 2015 to 2019.

 Page is also a founding investor of Planetary Resources, a space exploration, and asteroid-mining company. Originally established in 2009, the company was acquired by a blockchain firm in 2018 amid funding problems. He has also shown an interest in "flying car" companies, having invested in both Kitty Hawk and Opener. Shares of Google soared almost 50% in 2021, helping push both Page and Br in up the billionaire list.

 Mark Zuckerberg

•  Age: 37
•  Residence: California
•  Co-founder, CEO, and Chair: Meta (FB)
•  Net Worth: $124 billion
•  Facebook Ownership Stake: 13% ($115 billion)
•  Other Assets: $3.5 billion in cash.

 Mark Zuckerberg first developed Facebook (now Meta) alongside fellow students Eduardo Severin, Dustin Moskovitz, and Chris Hughes while attending Harvard University in 2004. As Facebook began to be used at other universities, Zuckerberg dropped out of Harvard to focus entirely on his growing business. Today, Zuckerberg is the CEO and chair of Meta, which had more than 2.9 billion monthly active users as of Q3 2021.

 Facebook is the world's largest social networking service, enabling its users to create a personal profile, connect with friends and family, join or create groups, and much more. As the website is free to use, most of the company's revenue is generated through advertising.

 Meta is also host to several other brands, including photo-sharing app Instagram, which it acquired in 2012; cross-platform mobile messaging service WhatsApp and virtual-reality–headset producer Oculus, both acquired in 2014; Workplace, its enterprise-connectivity platform; Portal, its line of video-calling devices; and No vi, its digital wallet for the Diem payment system.

 Zuckerberg and his wife, Priscilla Chan, founded the Chan Zuckerberg Initiative in 2015, with each of them serving as co-CEO. Their charity seeks to leverage technology to fix societal ills, such as improving the access and quality of education, reforming both the criminal justice system and the U.S. immigration system, improving housing affordability, and eventually eradicating all diseases.

 Sergey Brin

•  Age: 48
•  Residence: California
•  Co-founder and Board Member: Alphabet (G O O G)
•  Net Worth: $119 billion
•  Alphabet Ownership Stake: 6% ($102 billion total)
•  Other Assets: $14.7 billion in cash.

 What makes Google unique, compared to the other companies featured on this list, is that its co-founders are relatively close in terms of total wealth. Sergey Brin’s involvement in Google follows a similar path to Page’s. After the duo founded the company in 1998, he served as co-president alongside Page until Eric Schmidt took over as CEO in 2001. Similarly, after founding Alphabet in 2015, he acted as the holding company’s president before stepping down in 2019 when Sundar Pichai took over as CEO.

 In addition to being a highly popular search engine, Google also offers a suite of online tools and services, known as Google Workspace, which includes Gmail, Google Drive, Google Calendar, Google Meet, Google Chat, Google Docs, Google Sheets, Google Slides, and more.75 In addition to software, Google also deals in a wide variety of electronic devices, including its Pixel smartphones, its Pixelbook computers and tablets, its Nest smart home devices, and its Stadia gaming platform.

 He spent much of 2019 focusing on X, Alphabet’s moonshot research laboratory, which is responsible for innovative technologies like the Waymo self-driving cars and Google Glass smart glasses. He has also donated millions of dollars toward researching a cure for Parkinson’s and partnered with The Michael J. Fox Foundation to devise new drugs against LRRK2, one of the greatest genetic contributors to the disease.

 Warren Buffett,

•  Age: 91
•  Residence: Nebraska
•  CEO: Berkshire Hathaway 
•  Net Worth: $117 billion
•  Berkshire Hathaway Ownership Stake: 16% ($115 billion)
•  Other Assets: $1.13 billion in cash.

 The most famous living value investor, Warren Buffett filed his first tax return in 1944 at age 14, declaring his earnings from his boyhood paper route. He first bought shares in a textile company called Berkshire Hathaway in 1962, becoming the majority shareholder by 1965. He expanded the company to insurance and other investments in 1967. Now, Berkshire Hathaway is a half-trillion-dollar company, with a single share of stock (Class A shares) trading at more than $477,000 per share as of Jan. 18, 2022.

 Widely known as the Oracle of Omaha, Buffett made the majority of his fortune through purchasing shares in companies with easy-to-understand business operations. While many investors have been piling into tech companies, Buffett has opted for a more cautious approach, only buying from well-established companies that are easier to understand, such as IBM and Apple. He is also a noted Bitcoin skeptic. Additionally, Buffett has also outright purchased a lengthy list of companies over the years, including Dairy Queen, Duracell, GEICO, and Kraft Heinz.

 Outside of investing, Buffett has directed much of his wealth toward philanthropic endeavors. Between 2006 and 2020, Buffett gave away $41 billion—the majority of which went to either the Bill & Melinda Gates Foundation or his children’s charities. Buffett launched the Giving Pledge alongside Bill Gates in 2010.

 Steve Ballmer

•  Age: 65
•  Residence: Washington
•  Owner: Los Angeles Clippers
•  Net Worth: $111 billion
•  Microsoft Ownership Stake: 4% ($101 billion total)
•  Other Assets: Los Angeles Clippers ($2.63 billion private assets), $5.03 billion in cash. 

 Steve Ballmer joined Microsoft in 1980 after Bill Gates convinced him to drop out of Stanford University's MBA program. He was Microsoft's 30th employee. Ballmer went on to become CEO of Microsoft in 2000, taking over the position from Bill Gates. He held the position until he stepped down in 2014. As part of his tenure, he oversaw the 2011 purchase of Skype for $8.5 billion.

 Ballmer owns an estimated 4% of Microsoft shares, making him the largest individual shareholder of the tech company. In 2014, shortly after stepping down as Microsoft CEO, Ballmer purchased the L.A. Clippers basketball team for $2 billion.

 Ballmer lived down the hall from Bill Gates while the two were both attending Harvard University. Their "brotherly" relationship, as described by Ballmer, was strained, however, when Ballmer started pushing the tech company into hardware (e.g. Surface, Windows phone, etc.).

 Larry Ellison

•  Age: 77
•  Residence: Hawaii
•  Co-founder, CTO, and Chair: Oracle 
•  Net Worth: $107 billion
•  Oracle Ownership Stake: 40% ($71.3 billion)
•  Other Assets: Tesla equity ($15.5 billion public assets) and $17.2 billion in cash.

 After dropping out of the University of Chicago in 1966, Larry Ellison moved to California and worked as a computer programmer for several companies over the years. First, in 1973, he was an employee of the electronics company, where he met future partners Ed Oates and Bob Miner. Three years later, Ellison joined Precision Instruments, serving as the company’s vice president of research and development.

 By 1977, Ellison founded Software Development Laboratories (SDL) alongside Oates and Miner, which, two years later, released Oracle, the first commercial relational database program to utilize Structured Query Language. The database program proved so popular that SDL would change its name to Oracle Systems Corporation in 1982. Additionally, Ellison joined Tesla's board in Dec. 2018.

 Oracle is the second-largest software company and provides a wide variety of cloud computing programs as well as other software, such as Java and Linux, and the Oracle computing platform. The business has also grown through the acquisition of several major companies, including human resources management systems provider People Soft in 2005, customer relationship management applications provider in 2006, enterprise infrastructure software provider BEA Systems in 2008, and hardware-and-software developer Sun Microsystems in 2009.

(Source: Investopedia)