The plot below is the real yields. I didn't see an easy way to update the color bar, so read the '10' and '-10' as '>=10' and '<=-10'. Those are all percentages. To read it, simply pick a row for your starting year, and read-left to right to see how the investment performed. For example, if you start at 1928, then 1928 is 1 year, 1929 is 2 years, etc.

If you start at 1966 and check 1995 and see a value of 4.6%, that means that the real yield if you invested steadily for 30 years starting in 1996 is 4.6%. Hovering lets you see more detailed info.

Read below the plot for methodology.

I got yields from here and inflation from here. To calculate the values in the plot, I used the following algorithm:

1. start at 1928 with $100
2. multiply by 1928's yield
3. add an inflation-adjusted $100
4. calculate the rate that yields that future value with number of years since start and the annual investment
5. multiply by 1929's yield
6. add an inflation-adjusted $100
7. calculate the rate that yields that future value with number of years since start and the annual investment
8. repeat 4-7 until you hit 2018
9. start at 1929 with $100
10. repeat 2-8
11. repeat for all starting years up through 2018