Hard-to-beat performance and ultra-low costs are making Vanguard Group’s index mutual funds hard for investors to resist, and a little beneficial advice from multi-billionaire Warren Buffett is bringing money into Malvern by the bucketload.

Its S&P 500 index fund is raking in three times as much cash as it did last year, and its Total Stock Market Index has risen to become the world’s biggest mutual fund, according to a report in The Wall Street Journal. Overall, Vanguard is about to reach the $3 trillion milestone for assets.

“I’m firmly convinced it’s the better way to go,” securities lawyer Philip Henry said in the article. “I don’t believe fund managers can beat the market.”

Cost-wise, the expense ratio for the average Vanguard U.S. equity index comes in at 0.1 percent, well under the 0.7 percent of its rivals and the 1.3 percent of active managers.

Read more about Vanguard’s success and the trend toward passive management in The Wall Street Journal here.