Bill Gates, the world's most generous person, says that as long as he helps eradicate deadly diseases like polio and malaria, he doesn't care if he's forgotten after his death. Not that there's any chance of that: Gates has already given more than $28 billion, but said in his fifth annual letter for the Bill & Melinda Gates Foundation that the total amount invested is less important than precise measures of impact, like child mortality rates. Gates has been spreading his gospel to other billionaires near and far: he and good friend Warren Buffett recently added 12 non-Americans to their Giving Pledge, including the U.K.'s Richard Branson and India's Azim Premji, bumping the total to 105 high net worth individuals. He also partnered with Carlos Slim to build a new $25 million agricultural research center in Mexico. Gates' net worth increased $6 billion to $67 billion in the past year - with no help from the company he cofounded, Microsoft, in which he still has a 5% stock. Most of his fortune these days is spread across private equity, bonds, and stocks like hygiene tech firm Ecolab, Mexican TV broadcaster Televisa, and Latin America's largest beverage company FEMSA. In February, Gates said the only thing left on his bucket list was, "Don't die.