The stock market basically doubles every 10 years, says Ron Baron (Trades, Portfolio).
That equates to a return of about 6.2%, but if you add in dividends, the figure is closer to 8%.
Based on the rate the market has been going up, it might suggest that a short term correction is due soon. However, Baron thinks that you should stay invested and fight the fact that the power of your dollar is cut in half every 20 years.
