Imagine if one invested in a tracker fund that tracked the Dow Jones Industrial Index, 20 years ago:

The Dow 30 was at 9, 814. In December 1996

Now if one held that fund, today, 20 years on :-

The index is at 19, 843 in December 2016

The index has more than doubled in 20 years. With hindsight it was a one way bet. Your money has more than doubled, with dividends from these companies in the index. Praise to Jack Bogle.