Still identified by many people as the richest man in the world, William Gates III, Harvard's most famous dropout, now comes in second to Carlos Slim. "Common Sense" estimates the Microsoft founder to be worth $59 billion. His good friend and occasional business advisor, Warren Buffett, is the world's third richest man, believed to have a fortune of around $52 billion.
Gates has retired from most of his duties at Microsoft in order to focus on the Bill & Melinda Gates Foundation, the largest charitable foundation in the world. The foundation had $33.4 billion as of March 31, 2007, with almost $30 billion more on the way from Buffett, who has pledged to give away most of his great wealth.
Gates' fortune has fluctuated tremendously because much of it was tied up in Microsoft stock. His net worth peaked at around $100 billion during the height of the dot-com boom. Gates now sells 80 million shares of Microsoft stock a year, though half of his worth is still tied up in Microsoft [Source: Forbes]. Gates' investment diversification has made his net worth difficult to verify. Much of his non-Microsoft investments are managed by Cascade Investment, LLC, a private equity firm. The firm invests on his behalf in a wide range of companies, some of which, like the photography company Corbis, he owns.
With private and public investment soaking up much of the wealth of the world's mega-rich, the title of the world's richest person may continue to shift. No one individual has $30 or $40 billion in cash or gold, so the mega-rich can see their fortunes fluctuate up and down by billions of dollars a year. After all, Gates was once worth more than $100 billion, so "on paper" he's lost $41 billion. Most of Carlos Slim's fortune is tied up in the shares of the companies that he owns, which Slim says he has no intention of selling, so his net worth is prone to some fluctuation as well.
Reportedly, Slim has said he's not interested in competing to be the richest person in the world, but it's interesting to consider what actually grants a person that title. Is it who has the most wealth on paper? Or is it who has the biggest bank accounts, the most important investments, priceless art or the power to influence world affairs? Ownership can be a tricky question, too. Many heads of state, both ancient and modern, have had the resources of an entire kingdom or empire available to them, but may not personally "own" them. Look no farther than the royal families of some Middle Eastern states. The vast oil wealth these countries garner is frequently distributed between a variety of state-owned and private companies, royal family members, investment groups and offices of the government. At times, it can be difficult to pinpoint where the government ends and private ownership begins.
It's possible to identify who was likely the richest American ever. John D. Rockefeller (1839-1937) was America's first billionaire. At one point, his wealth comprised 1.53 percent of the U.S. gross national product (GNP), something not even Bill Gates, at less than a quarter of a percent of U.S. GNP, can claim.
For more information about Carlos Slim, the mega-rich and important charitable foundations, check out the links on the next page.