Berkshire Hathaway CEO Warren Buffett has accumulated the most wealth of any billionaire this year, according to a study from wealth research firm Wealth-X.

From Jan. 1 to Dec. 11, the legendary investor increased his net worth by $12.7 billion, or 27.4 percent, to a total of $59.1 billion. That's a gain of $37 million a day.

Berkshire owns both publicly and privately held companies. The Standard & Poor's 500 Index increased 25 percent from the beginning of the year through Dec. 11.

Editor’s Note: Obama Donor Banned This Message (Shocking)

Berkshire's biggest stock holdings as of the third quarter included Wells Fargo, Coca-Cola, American Express, International Business Machines and Procter & Gamble.

The top 10 billionaires on Wealth-X's list for increasing their wealth this year averaged a gain of 41.6 percent, far outstripping the S&P 500's return.

Microsoft Chairman Bill Gates placed second on the list, with a net worth gain of $11.5 billion, or 18.8 percent, to $72.6 billion. Gates is the wealthiest man on the list.

Sheldon Adelson, CEO of Las Vegas Sands, had the third biggest net worth ascent — $11.4 billion, or 47.7 percent, to $35.3 billion.

"The gains were fueled almost entirely by rising stock prices, which boosted the value of company shares held by founders and corporate chiefs," writes CNBC's Robert Frank.

"And the wealth was spread throughout all industries, suggesting that the broad stock market gains have been the chief wealth driver this year — rather than industry-specific gains in tech, energy or other sectors."

Editor’s Note: Obama Donor Banned This Message (Shocking)

Related Stories:

• World's 100 Wealthiest Add $200 Billion as Global Markets Rise
• Rich Get Richer Throughout the States