The ranks of the world’s billionaires continue to scale new heights–and stretch to new corners of the world. Our global wealth team found 1,645 billionaires with an aggregate net worth of $6.4 trillion, up from $5.4 trillion a year ago. We unearthed a record 268 new ten-figure fortunes, including 42 new women billionaires, another record. In total, there are 172 women on the list, more than ever before and up from 138 last year.

Bill Gates is back on top after a four-year hiatus, reclaiming the title of world’s richest person from telecom mogul Carlos Slim Helu of Mexico, who ranked No. 1 for the past four years. Gates, whose fortune rose by $9 billion in the past year, has held the top spot for 15 of the past 20 years. Spanish clothing retailer Amancio Ortega (best known for the Zara fashion chain) retains the No. 3 spot for the second year in a row, extending his lead over Warren Buffett, who is again No. 4. American gambling tycoon Sheldon Adelson, who added $11.5 billion to his pile, makes it back into the top ten for the first time since 2007. Another first: A record net worth of $31 billion was needed to make the top 20, up from $23 billion last year.

The year’s biggest dollar gainer was Facebook’s Mark Zuckerberg, whose fortune jumped $15.2 billion, to $28.5 billion, as shares of his social network soared. Tech, and more specifically Facebook, helped propel numerous fortunes lately. The company’s COO, Sheryl Sandberg, joins the ranks for the first time, as does Facebook’s longtime vice president Jeff Rothschild. Also, thanks to a $19 billion deal (including restricted stock) with Facebook, WhatsApp founders Jan Koum and Brian Acton join the ranks of Silicon Valley’s wealthiest for the first time. They are 4 of 26 newcomers whose fortunes come from technology, 10 of whom are American, including Dropbox CEO Drew Houston and Workday cofounder Aneel Bhusri.

Thanks to the tech boom, and strong stock market, the U.S. once again leads the world with 492 billionaires, followed by China with 152 and Russia with 111. But wealth is spreading to new places. We found billionaires for the first time in Algeria, Lithuania, Tanzania and Uganda. Also for the first time, an African, Aliko Dangote of Nigeria, breaks into the top 25. Worth $25 billion, he moves up 20 spots.

Roughly two-thirds of the billionaires built their own fortunes, 13% inherited them and 21% have been adding on to fortunes they received. Other notable newcomers include World Wrestling Entertainment CEO Vince McMahon, fashion king Michael Kors and Denise Coates of UK online betting firm Bet365.

Still not all countries–or tycoons–had good years. Turkey lost 19 billionaires due to soaring inflation, a sagging stock market and a declining value in its currency. Indonesia, whose currency tumbled 20% against the dollar, now has 8 fewer ten-figure fortunes. Altogether 100 people dropped out of the ranks, while another 16 passed away.

Methodology

This is our 28th year publishing the Forbes Billionaires list. Though we’ve been at it a long time, it is never an easy task. Our reporters dig deep and travel far. To compile net worths, we value individuals’ assets–including stakes in public and private companies, real estate, yachts, art and cash–and take into account estimates of debt. We attempt to vet these numbers with all billionaires. Some cooperate; others don’t. We also consult an array of outside experts in various fields.

The Forbes Billionaires ranks individuals rather than large, multi-generational families who share large fortunes. So Maja Oeri, who has a disclosed stake in pharmaceutical firm Roche, makes the list, but her eight relatives who, with a nonprofit foundation, share a multi-billion fortune do not. In some cases we list siblings together if the ownership breakdown among them isn’t clear, but here, too, they must be worth a minimum of $2 billion together, or equivalent to $1 billion apiece, to make the cut. We split up these fortunes when we get better information, as we did with the Canada’s Irving brothers this year. Children are listed with their parents when one person is the founder and in control. Those fortunes are identified as “& family.”

We do not include royal family members or dictators who derive their fortunes entirely as a result of their position of power, nor do we include royalty who, often with large families, control the riches in trust for their nation. Over the years Forbes has valued the fortunes of these wealthy despots, dictators and royals but have listed them separately as they do not truly reflect individual, entrepreneurial wealth that could be passed down to a younger generation or truly given away.

Our estimates are a snapshot of wealth on Feb. 12, when we locked in stock prices and exchange rates from around the world. If a stock market wasn’t open on that day, the stock price is from the previous trading day.

By Kerry A. Dolan and Luisa Kroll, Forbes Staff. Forbes Magazine. Published: March 3rd, 2014