I used years just to get a rough feel. Even in the U.S., you don't get consistency. Some folks skip grades, dual major or take night classes, etc. I'm well aware that foreign educational plans don't necessarily map well to U.S. standard durations.
I'm actually surprised at how few 18 and younger have responded. Do they find ENWorld to be too mature? There does seem to be a lower incidence of "neener-neener" posts compared to other boards.
Note: YES, I know, there are some very mature teenagers out there. I'm speaking in generalizations.
Also, the financial perception things is interesting. I wonder how much of it is based on perception bias vs. the fact that the hobby encourages spending money vs. the higher levels of education tend to correlate with higher incomes?