I dont think we are comparing apples with apples hear although I can't quite figure out why! The figures I quoted via the ARG reports were both factoring in "accumulation" and presuming dividends were reinvested (just look under the document titled "shareholder letter regarding 2018 results) and on a 15 year basis the asx 200 accumulation index returned 9.6 percent while Argo returned 8 percent (including dividends) while on a 10 year basis it was 6.4 percent for the ASX and 5.5 percent for Argo.
So I definitely don't think your "wrong" I just can't figure out what your chart represent's that's different than these figures.
I am pretty suprised by the big gap in 15 year performance as that 1.6 percent gap makes a big difference over that time frame.
I do feel that if we get a downturn the performance figures might improve somewhat as I would expect the ARG portfolio to decline less than the overall market being so conservative.
In my experience as an AFI shareholder (the very first shares I ever bought just in time for the financial crisis in 2007!) they under perform quite significantly in good times and over perform in bad times while managing to keep their dividend steady.
ARG Price at posting:
$7.92 Sentiment: Hold Disclosure: Not Held