It's interesting, and I'm only on page 16 but some things do come to mind like many of the participant may not have been investing in their prime earning years. Also, "higher levels of educations are associated with a much lower likelihood of overconfidence as are being male and white".
Obviously that is pointed at the fact that those who invested because they had the money or it was their role in the family (educated white males) perform better. I suspect it's just that they are more familiar in general. I suspect everyone who reads on bogleheads is probably more advanced and familiar with financial topics that even the white males in their study who didn't suffer overconfidence as much due to the familiarity factor.
And other things like "the strongest age effect occurs for the questions on the deductibility of interest and the use of money market accounts". I don't know about you, but I don't think I will have a mortgage in my old age and probably wouldn't spend much time on answering the question. And I suspect that renters or those who own their home might be the same.
Anyway, Bogleheads will knock your overconfidence pretty fast. Try posting something that is not universally considered perfect in a thread and see how it goes.
The area I think I will suffer in is insurance. Health care in America is mindbogglingly complex. Perhaps that is a strategy employed by insurers to take advantage of us.
I don't have perfect use of rewards cards now either. Yeah, I use them them but don't care to try to optimize my spending to earn points. It's just who cares.
I don't see anything about people not doing their taxes right or investing poorly in the study. It says the most overconfident don't optimally refinance or choose a reward credit. Not such a concern that I need an advisor. Should I extrapolate from that to that I can't manage my assets? I am not sure.
Again, getting the right insurance policy seems a nightmare.