I've spent a bit of time browsing Les Antman's excellent personal finance forums and have come to the conclusion that splitting my equity portfolio 50/50 US Total Mkt & Total Int'l via low-cost index funds is the way to go.
I know that there have been many suggestions for adding various features to the FireCalc SWR machine, but I suspect that we might see a meaningful increase in SWR's if we were able to add in various amounts of international equites. I also know that a frequently cited difficulty with evaluating international equities from a historical perspective is the dearth of solid data prior to 1970 or so.
I mentioned this in a thread on Les' Retirement Forum, but he countered that accurate longer term (~100 years) of international equity returns data is available:
Is there any chance you could have a look into the practicality of including an International index in FireCalc? In other threads Les points out that a US investor in 1929, if he had split his porfolio 50/50, would have been "whole" within 5 years (allowing for deflation). Same deal with a Japanese investor in 1990. My guess is that a 50/50 allocation might have improved SWR's in the troublesome period in the 1960's as well.