Gyroscopic Investing

Hello!
I am new to investing but I have already learned a lot from you all. Although this is my first post, I have been reading here for awhile.

I see that one way to implement the PP is to use 25% of each of the following ETFs:  VTI, SHY, TLT and IAU.  But when I look at the annual performance of each of these ETFs I see percentages that are sometimes quite different from the historical returns reported in the Cash FAQ thread article:
https://web.archive.org/web/20160324133 ... l-returns/

I was just wondering why the annual returns I see for these four ETFs are often so different from the historical returns reported in this article. 

The figures in the article are from the Simba spreadsheet which gives total return (NAV plus dividends and interest) of Vanguard funds.  Many data sources only quote NAV changes and thus will have different figures.  There will also be a discrepancy if you look at funds that track a different index than the corresponding Vanguard fund.  In particular Vanguard's long term bond fund has a shorter duration than TLT and other alternatives.