(Bloomberg) -- High-frequency trading has been good to billionaire Ken Griffin.

His Citadel LLC returned more than 300% in a fund started as a high-frequency strategy in late 2007, according to two people familiar with the Chicago-based money manager. The $830 million pool, which added other strategies in recent years, beat the 44% gain of the U.S. stock market in the six years through 2013 as well as Griffin’s two main hedge funds, which together have $8.8 billion in assets and rose 45% in the period.

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