Chart illustrating the average stock market return for 20 years is 4.1%
Adam Rifkin stashed this in Charts!
This is one of the greatest charts ever made.
“Market returns are more volatile than most people realize,” Mr. Easterling said, “even over periods as long as 20 years.”
I found this chart from a HackerNews discussion talking about what is the number halfway between 1 and 9: http://news.ycombinator.com/item?id=4626683
Hint: it could be 5 -- or it could be 3. Logarithms are actually more intuitive for many. http://web.mit.edu/newsoffice/2012/thinking-logarithmically-1005.html