With great wealth comes the power to effect change. But more than money determines how much influence a billionaire wields.
In compiling our first power ranking for billionaires, we weighed their political connections, the size and scope of their businesses and investments, their media coverage, their philanthropic pursuits and, of course, their net worth.
Here are the power rankings. The second number is the person's ranking on Forbes' list of the world's richest people:
1) Bill Gates, $40.7 billion, Rank: 1
Microsoft's operating software drives 93 percent of the world's desktop computers. The world's richest man is also its biggest giver: more than $1 billion annually, much to vaccine research.
2) Warren Buffett, $30.5 billion, Rank: 2
The Oracle of Omaha owns 36 percent of Berkshire Hathaway, a property/casualty company with an immensely profitable side line managing its portfolio of stakes in blue chips like Gillette and Coca-Cola. He vows to leave his wealth to charity.
3) Silvio Berlusconi, $5.9 billion, Rank: 45 (tie)
Italy's prime minister owes much of his influence to Fininvest, his investment firm, which owns 49 percent of Mediaset, Italy's largest television network. He also has interests in banking, insurance and publishing.
4) Rupert Murdoch, $5.5 billion, Rank: 54
While rivals circle the drain, Murdoch's News Corp. remains buoyant on hits like Fox TV's Joe Millionaire. The media baron's empire also includes movies and publishing, but satellite television gives him his global reach. He hopes to have better luck in the second round of his prizefight for satellite broadcaster DirecTV.
5) Li Ka-shing, $7.8 billion, Rank: 28
Centered on the conglomerate Hutchinson Whampoa (telecom, port services, real estate), Li's empire spans 41 countries and accounts for 13 percent of Hong Kong's stock market value. Asia's richest man has invested $7 billion in Mainland China and built 400 miles of roads and bridges.
6) Prince Alwaleed, $17.7 billion, Rank: 5
This Saudi prince's influence reaches far beyond the Middle East. Citigroup's largest individual investor has met with heads of states of more than 20 countries, including Russia, the United Kingdom and China.
7) Mikhail Khodorkovsky, $8 billion, Rank: 26
He's the head of Russia's second-largest oil company, Yukos,which helps keep world energy prices down by boosting oil exports in face of OPEC protests. Russia's richest man is also leading the charge in making the country's murky business affairs more transparent.
8) Robson Walton, $16.5 billion, Rank: 7
Eldest son of Sam Walton controls family's 38 percent stake in Wal-Mart, the world's largest retailer: some 3,200 stores in the United States, nearly 1,200 stores abroad. Sales: $244 billion. The company might beef up its European presence with a bid for U.K. grocer Safeway.
9) Carlos Slim Helú, $7.4 billion, Rank: 35
Known for his investments in U.S. retailers like Saks and Circuit City, Helú also has holdings representing a third of the Mexican Bolsa. He is plowing millions into rejuvenating Mexico City and has hired former New York Mayor Rudolph Giuliani to curb the city's crime. He is also tight with Mexico's top political up and comers.
10) Azim Premji, $5.9 billion, Rank: 45 (tie)
He owns 84 percent of Bangalore-based Wipro, India's largest technology concern. Wipro is a leader in the lucrative business of shifting white-collar jobs from the U.S. and Europe to Asia.
For more, go to Forbes.com..