The chart page doesn't explain things very well, so it takes a bit to unpack, but the point of the chart is actually to give a better idea of comparative performance over a time period rather than focusing on a particular number like average return. Basically it's dividing the current value of one portfolio by the other at each point. The ratio shows the ebb and flow of the two portfolios against each other. John Bogle's speech [1] and this forum [2] probably explain it better.
[1] http://www.vanguard.com/bogle_site/sp20020626.html
[2] https://www.bogleheads.org/forum/viewtopic.php?t=138973
EDIT: cleaned up the first paragraph.
My claim with respect to this thread is that there is a strategy that outperforms in certain conditions like the 2008 selloff and 1970s inflation and does so without the risk of losing the gains as soon as the market turns around.
Relative to stocks or 60/40 during a bull market, it doesn't look so good, but it still generates positive returns, holding for some time any edge gained during the earlier conditions.
The overall result is a smooth climb, so I do claim it works well (enough) all the time. I don't claim absolute outperformance long term.
The best chart for what I'm trying to show is beneath the data table in [1]. And the Envy calculator at [2] has great data back to 1972 for different assets (and lets you change the start date).
[1] http://www.crawlingroad.com/blog/2008/12/22/permanent-portfo...