The 20 most generous people in the world

Lifetime donations: $1 billion

Net worth: $6.2 billion

Generosity Index: 16%

Paris-born, Iranian-American Pierre Omidyar is cofounder and current chairman of eBay.

In 1998, he and his wife, Pamela, established the Omidyar Foundation, an organization that now includes Omidyar Network, HopeLab, Humanity United, and Ulupono Initiative. The organization donates to a diverse range of causes, including entrepreneurship, human rights, food and energy, and games and technology. In 2012, Omidyar and his wife joined the Giving Pledge initiative started by Warren Buffett and Bill Gates, promising to donate most of their wealth to charities.

In August 2015, Omidyar reportedly sold 10% of his shares in eBay to undisclosed charities — a stock gift valued at nearly $270 million.

Source: Wealth-X

Lifetime donations: $1.1 billion

Net worth: $18.9 billion

Generosity Index: 6%

Michael Dell is the chairman and CEO of Dell computer company. Since 1999, he's been the director of the Michael and Susan Dell Foundation, which gives primarily to education, social and human services, arts and culture, and community-development causes.

Earlier this year, the foundation pledged to donate $25 million to fund the construction of a new teaching hospital in Austin, Texas.

Source: Wealth-X

Lifetime donations: $1.2 billion

Net worth: $12.3 billion

Generosity Index: 10%

James Simons is chairman of investment-management company Renaissance Technologies, one of the largest and most successful hedge fund companies in the world with $65 billion in assets. Simons served as the company's CEO until retiring in 2009.

Twenty-one years ago, Simons and his wife Marilyn established the Simons Foundation, which primarily supports educational causes. Since then, the couple has founded two additional organizations in memory of their two sons who died in 1996 and 2003: The Paul Simons Foundation gives to social and educational causes, and the Nick Simons Foundation trains rural healthcare workers in Nepal and gives to humanitarian and social causes.

Simons has also donated $30 million to autism research and has pledged to donate $100 million more.

Source: Wealth-X

Lifetime donations: $1.2 billion

Net worth: $2.1 billion

Generosity Index: 57%

Ted Turner, former CEO of Turner Broadcasting System (TBS) and vice chairman and director of AOL Time Warner, is the current chairman of Turner Enterprises, a diversified holding company.

Turner also serves as trustee of the Turner Global Foundation and chairman of the Turner Foundation, which both donate to community development and environmental and wildlife conservation causes.

The UN Foundation is also a chief recipient of Turner's donations. In 1997 he pledged $1 billion to the foundation, which promotes causes related to women and population, children's health, environment, world peace, and security.

Source: Wealth-X

Lifetime donations: $1.2 billion

Net worth: $940 million

Generosity Index: 128%

Jon Huntsman Sr. is the founder and executive chairman of Huntsman Corporation, a chemical product manufacturer.

Huntsman has reportedly survived prostate and mouth cancer and, as a result, established the Huntsman Cancer Institute at the University of Utah. Many of his charitable donations have been to colleges and cancer-research centers. He and his wife also agreed to join Buffett's Giving Pledge, promising to donate 50% of their wealth.

Source: Wealth-X

Lifetime donations: $1.4 billion

Net worth: $26.6 billion

Generosity Index: 5%

Li Ka-shing is a global investor in disruptive technology and one of the richest men in Asia.

In 1980, he established the Li Ka-shing Foundation to support education, healthcare, culture, and community-related causes. The foundation's biggest project to date was funding Shantou University, the only privately funded public university in China. Li has also made personal donations to the China Foundation for Disabled Persons and flood-victim relief in China.

Source: Wealth-X

Lifetime donations: $1.6 billion

Net worth: $40.7 billion

Generosity Index: 4%

Facebook founder and CEO Mark Zuckerberg is one of the youngest self-made billionaires in the world. The social-media mogul has signed the Giving Pledge and promises to donate at least half of his wealth in his lifetime.

Last year, Zuckerberg and his wife Priscilla famously donated $25 million in the fight against Ebola. Through the Silicon Valley Community Foundation, Zuckerberg gave $75 million to San Francisco General Hospital.

They're also focused on education: The pair gave $120 million to improve Bay Area schools, and before that, donated $100 million worth of Facebook shares to a New Jersey public-school system.

Source: Wealth-X

Lifetime donations: $2 billion

Net worth: $17.3 billion

Generosity Index: 12%

Paul Allen, cofounder of Microsoft, now serves as the chairman of Vulcan, his private-investment company.

As chairman of the Paul G. Allen Family Foundation, he's given millions to global-health causes, including $5 million to Seattle BioMed, $4 million to Global FinPrint, a conservation project focused on the preservation of sharks worldwide, and $7 million in grants to Alzheimer's research.

Source: Wealth-X

Lifetime donations: $3 billion

Net worth: $37.7 billion

Generosity Index: 8%

Michael Bloomberg is the founder and CEO of Bloomberg media company and founder of the Bloomberg Foundation, which gives primarily to educational, healthcare, and environmental causes. Recipients of the foundation's donations include John Hopkins University, World Lung Foundation, World Health Organization, Sierra Club Foundation, and John Hopkins Bloomberg School of Public Health.

Most recently, Bloomberg launched a $42 million "What Works Cities" initiative aimed at helping 100 mid-sized cities to make better use of data and evidence through his philanthropic arm, Bloomberg Philanthropies.

Source: Wealth-X

Lifetime donations: $3.3 billion

Net worth: $9.3 billion

Generosity Index: 35%

George Kaiser, chairman of BOK Financial Corporation, also founded the George Kaiser Family Foundation, which gives to educational, health, religious, social, and community-development-related causes, including the Tulsa Community College Foundation, Oklahoma City Educare, National Energy Policy Institute, the Tulsa Community Foundation and the University of Tulsa.

In 2010, Kaiser joined the Giving Pledge, vowing to donate half of his fortune to charity.

Source: Wealth-X

Lifetime donations: $3.3 billion

Net worth: $7.3 billion

Generosity Index: 45%

Through The Broad Foundation, KB Home cofounder and former SunAmerica CEO Eli Broad invests in public education, science, and the arts.

The organization operates as two entities, The Eli and Edythe Broad Foundation and The Broad Art Foundation, both of which aim to improve communities and advance entrepreneurship.

A resident of California, Broad gives back to his home state — and the arts — through donations to the Museum of Contemporary Art, Los Angeles and the Los Angeles County Museum of Art.

Source: Wealth-X

Lifetime donations: $27.3 billion

Net worth: $4 billion

Generosity Index: 15%

One of the richest self-made billionaires in the world and the chairman of Grupo Carso, Carlos Slim Helú's primary philanthropic efforts occur through his Fundación Carlos Slim Helú.

The foundation has invested $100 million in the World Wildlife Fund toward efforts to conserve Mexico's natural environment, and in 2012, it gave $3 million to help provide internet to Latino families living in the US, in addition to many other donations to international organizations.

Slim Helú also serves as chairman of the Telmex Foundation, which strives to improve the quality of life in Mexico, his home country.

Source: Wealth-X

Lifetime donations: $5 billion

Net worth: $6.5 billion

Generosity Index: 77%

Gordon Moore cofounded Intel in 1968, but these days he is focused on philanthropy. He retired from his corporate positions in 2006, and currently runs the Gordon and Betty Moore Foundation with his wife.

The foundation aims to make an impact in environmental conservation, patient care, science, and the San Francisco community, and has wide-spanning programs that include everything from the Marine Conservation Initiative to the Thirty Meter Telescope.

Source: Wealth-X

Lifetime donations: $5.7 billion

Net worth: $590 million

Generosity Index: 966%

Back in 1957, Sulaiman bin Abdul Aziz Al Rajhi cofounded Al Rajhi Bank with his three brothers. It grew into one of the world's largest Islamic banks and earned Al Rajhi a 10-digit net worth.

But in 2013, he shifted his focus toward philanthropy and endowed his holdings in the bank to Sulaiman bin Abdul Aziz Al Rajhi Endowments Holding Company, which supports educational, religious, health, and social causes, including the Arab Institute for Arabic Language, National Guard Health Affairs, and the Sheikh Sulaiman bin Abdul Aziz Al Rajhi Mosque in Riyadh, Saudi Arabia.

Source: Wealth-X

Lifetime donations: $6.3 billion

Net worth: $1.5 million

Generosity Index: 420,000%

Known as the "James Bond of philanthropy," retail magnate Chuck Feeney is on a mission to give away his entire fortune — and with his current net worth down to $1.5 million, it seems he's succeeded.

The Atlantic Philanthropies, Feeney's foundation, supports education, science, healthcare, and civil-rights causes across several countries, including the US, Vietnam, and Bermuda.

Source: Wealth-X

Lifetime donations: $8 billion

Net worth: $15.9 billion

Generosity Index: 50%

In addition to serving as the chairman of Indian consulting and IT company Wipro, Azim Premji is the founder and chairman of the Azim Premji Foundation, which works to reform India's school and examination systems.

The organization operates through Premji's earmarked Wipro stock, and has introduced initiatives such as the Computer Aided Learning program, which provides computer training in 18 languages, and Azim Premji University, a nonprofit university that awards degrees in teacher training.

Source: Wealth-X

Lifetime donations: $8 billion

Net worth: $24.4 billion

Generosity Index: 33%

George Soros, the retired founder of Soros Fund Management, currently serves as the chairman of the Open Society Foundations, a network of foundations he founded in 1979, which primarily donate to international causes, community development, social services, health, and education.

Open Society is best known for its focus on human rights. Soros' first act with the organization involved providing scholarships to black South Africans under apartheid.

Source: Wealth-X

Lifetime donations: $21.5 billion

Net worth: $61 billion

Generosity Index: 35%

The chairman and CEO of holding company Berkshire Hathaway, Warren Buffett is not only one of the wealthiest people in the world, he's also one of the most charitable.

In 2006, Buffett vowed to donate 85% of his wealth to the Bill & Melinda Gates Foundation, as well as other foundations set up by family members.

And in 2011, the Oracle of Omaha partnered with Gates in creating the Giving Pledge, a program that commits wealthy individuals to donating a large percentage of their wealth to charitable causes.

Source: Wealth-X

Lifetime donations: $27 billion

Net worth: $84.2 billion

Generosity Index: 32%

While he is best known as the cofounder of Microsoft, Bill Gates now focuses most of his time on philanthropy, running the Bill & Melinda Gates Foundation alongside his wife.

The foundation issues grants for initiatives and programs across the globe, focusing on agricultural development, emergency relief, global libraries, urban poverty, global health, and education.

Since its inception, the foundation has donated millions to organizations that include the GAVI Alliance; the World Health Organization; The Rotary Foundation; The Global Fund to Fight AIDS, Tuberculosis, and Malaria; and UNICEF.

Source: Wealth-X