Jack Bogle (founder of Vanguard) has said numerous times on various media and print, the "buy and hold" strategy will outperform most active managers and investors over the long term. Here's a good article regarding Bogle and some commentary regarding index investing.
http://www.wsj.com/articles/jack-bogle-the-undisputed-champion-of-the-long-run-1472855372
There is truth to it, but vanguards real outperformance came from its extremely low fees. It has funds that only charge 7bps/year!
