The richest people on the planet got even richer in 2013, adding $524 billion to their collective net worth, according to the Bloomberg Billionaires Index, a daily ranking of the world’s 300 wealthiest individuals.

The aggregate net worth of the world’s top billionaires stood at $3.7 trillion at the market close on Dec. 31, according to the ranking. The biggest gains came in the technology industry, which soared 28 percent during the year. Of the 300 people who appeared on the final ranking of 2013, only 70 registered a net loss for the 12-month period.

“The rich will keeping getting richer in 2014,” John Catsimatidis, the billionaire founder of real estate and energy conglomerate Red Apple Group Inc., said in a telephone interview from his New York office. “Interest rates will remain low, equity markets will keep rising, and the economy will grow at less than 2 percent.”

Bill Gates, the founder and chairman of Redmond, Washington-based Microsoft Corp., was the year’s biggest gainer. The 58-year-old tycoon’s fortune increased by $15.8 billion to $78.5 billion, according to the index, as shares of Microsoft, the world’s largest software maker, rose 40 percent.

Gates recaptured the title of world’s richest person on May 16 from Mexican investor Carlos Slim. Gates’s fortune has also benefited from a rally in stock holdings that include the Canadian National Railway Co. and sanitizing-products maker Ecolab Inc., which rose 34 percent and 45 percent respectively.

Most of Gates’s assets are held in Cascade Investment LLC, an entity through which he owns stakes in about three dozen publicly traded companies and several closely held businesses, including Four Seasons Hotels and Resorts and Corbis Corp., a photo-archive company. Less than a quarter of Gates’s fortune is held in Microsoft. He’s donated $28 billion to the Bill & Melinda Gates Foundation.

John Pinette, a spokesman for Gates, declined to comment. (Bloomberg)