Most things can’t be measured in any meaningful way.
Dear Hipster: I like to think of myself as an expert on certain topics. For example, I know more about DC wiring than most electricians, at least, the ones who primarily do residential AC work. Yet, I would have a hard time publically proclaiming to be an expert on DC wiring because I have no proof except the sum of my experiences. It’s not like life hands out certificates. Ultimately, how does one arrive at a place in life where “expert” status unequivocally attaches? — Stan
You fake it till you make it, bro. Every time. Anyone is an expert on anything, at least till a real expert comes in and proves you wrong. So long as you’re not routinely getting your ass handed to you on matters of expertitude, you must have mustered up the relevant level of expertise to pass as a credible expert. Anyway, most things like this can’t be measured in any meaningful way, on account of the glaring absence of credible certification that you already identified.