Not too long ago the long term rolling returns for the S&P 500 where still somewhere around this number. This article [1] is from 2012, not much has changed in the last four years.

"The average 30-year rolling total return for the S&P 500 starting with 1926, is 2,478% or 11.21% annualized (geometric mean). There were several 30-year periods that had annual returns between 8% and 10%."

Having said so, past returns don't guarantee anything for the future. They might give you an indication though.

[1]: http://allfinancialmatters.com/2012/08/29/sp-rolling-total-r...

Edit: Here's [2] a better (?) graph of the S&P 500 with the 30 year rolling returns, inflation adjusted and dividends reinvested. Source[3]

[2]: http://imgur.com/Ja1xOcA [3]: http://redd.it/3fsdex