I’d be really curious to hear more about this from people who run calibration exercises. I’ve heard of dramatic overconfidence but not underconfidence. I’m sure it exists.
I did Metaculus predictions for a few months and learned that I was in the category of people who need to increase their confidence slightly. I might also just have overcorrected after reading superforcasting. Generally it is hard to be calibrated on really small probabilities or to give 99% confidence intervals for quantities you know little about, so if you do those with calibration training exercises you will almost definitely come up short unless you already know this is hard in advance. Just don’t use probabilities below 1% if you are just getting started with that calibration stuff etc. because reading comprehension and other mistakes get you.
I don’t have a great personal sense. I think I read somewhere, but don’t remember exactly where that it is ~20% (could have been Tetlocks book). I guess the few times I did calibration training with people is compatible with that number or an even lower number.