I have a load of my pension money in an S&P500 tracker http://www.hl.co.uk/funds/fund-disc...ts/h/hsbc-american-index-class-c-accumulation when you look at the performance of the S&P500 since 1970 https://en.wikipedia.org/wiki/S&P_500_Index the annual return is quite decent. There are figures going back 90 years and if you adjust for inflation its about 7% growth over 90 years even including the crashes http://www.investopedia.com/ask/answers/042415/what-average-annual-return-sp-500.asp
7% is about the average long term returns in most markets. You have to be careful o be sufficiently diverse in investments and hope you don't have to cash out in a recession though. People like to talk about the 30% gains they made but they don't like to talk about those 25-30% losses they made just previously!