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. The biggest gains came in the technology industry, which soared 28 percent during the year. 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. Slim lost $1.4 billion during 2013. His America Movil SAB, the largest mobile-phone operator in the Americas, dropped 12 percent in the first three months of the year after Mexico's Congress passed a bill to quash the billionaire's market dominance. Sheldon Adelson, founder of Las Vegas Sands Corp., the world's largest casino company, was the second-biggest gainer in 2013, adding $14.4 billion to his net worth as the company's shares rose 71 percent.