There’s good reason why Warren Buffett is widely viewed as one of the most successful investors in the world. This past year, the Oracle of Omaha made about $37 million a day, topping a list of billionaires who made the biggest financial gains in 2013, a new study shows.

The legendary billionaire and philanthropist finished 2013 with a net worth of $59.1 billion, up from $46.4 billion at the beginning of the year, according to a wealth-analysis study by Wealth-X and UBS. The number of billionaires in the world grew between July 2012 and June 2013 with total wealth rising by 5.3%. Since the market’s March 2009 lows in the wake of the global financial crisis, billionaires have seen their total wealth more than double from $3.1 trillion to $6.5 trillion.