I'm using the S&P 500 data provided by Robert Shiller which goes back to 1871.
I've then calculated the percent return for each month, the simple arithmetic average is 0.43%. Calculating the compound annual growth rate from 4.44 to 1550.83 over 1707 months results in 0.34%.
Both of these values are significantly below what I would expect of at least around 0.5%, which would be roughly 6% annually.
Am I doing a some calculations wrong? Is this data not appropriate? Is the notion of 6% long-term average for the stock market incorrect?
Edit: Another way from framing my question might be: how do I calculate the values shown at MoneyChimp on my own? I'm happy to use raw data other than the spreadsheet above.