Bill Gates has reclaimed the top ranking in Forbes' magazine's list of world billionaires, ending Mexican communications magnate Carlos Slim Helu's four-year tenure as the richest man in the world.

The net worth of the Microsoft founder and philanthropist soared to $76 billion in 2013, according to Forbes, thanks to rising Microsoft shares. That eclipsed the $72 billion worth of Slim, who is perhaps best known in the United States for his ownership stake in The New York Times.

Charles and David Koch, brothers and owners of Koch Industries, saw their fortunes increase to $40 billion each, tying them for sixth richest in the world. The Koch brothers are top donors to Republican candidates and conservative causes. So is Sheldon Adelson, the seventh richest man in the world with $38 billion in Forbes' estimation.

The biggest gainer in the 2014 list was Mark Zuckerberg, the founder of Facebook, who rose from 66th to 21st on the list in one year as his net worth roughly doubled to $28.5 billion. Zuckerberg ventured further into the political sphere in 2013 than in previous years in an effort to boost comprehensive immigration reform.

George Soros, the Hungarian-born hedge fund manager who contributes to many left-leaning political causes in the U.S., also moved up the list, from 30 to 26, following a strong investing performance. The 83-year-old is worth $23 billion.

Overall, the aggregate net worth of the world's 1,645 billionaires rose by $1 trillion to $6.4 trillion, by Forbes' count.

The U.S. leads the world with 492 billionaires, followed by China with 152 and Russia with 111.

Two-thirds of the members of the Forbes' lists made their own fortunes. Thirteen percent inherited their riches, and another 21 percent "have been adding on to fortunes they received," according to Forbes.