why is past return data used but not past investment costs? and why is past foreign data not included? Past commissions were higher, and surely in the past some investor in the U.S. owned a few failed Argentine bonds. The more academic articles I read, the lower past average returns seem to fall.
I believe that the reason Foreign Data is not included is that it is simply not available in the same accurate form that the US data is.
As far as investment costs. FIRECalc will let you plug in any investment costs that you would like and see if your portfolio would have survived in past periods.
Have you tried FIRECalc yet?