For instance, the S&P 500 returned an average of 10.28% a year from 1985 to 2015. At this rate, your money doubles every seven years. Thanks to the power of compounding, you’d have made a killing just by owning an index fund that tracked the S&P 500 over those 30 years. Let’s say you’d invested $50,000 in 1985. How much would it have been worth by 2015? The answer: $941,613.61. That’s right. Almost a million bucks!
