> 1. That's not a bad percentage at all actually. I would say that is as its should be; it would not make sense for jobs to involve a huge amount of knowledge from multiple fields, unless your job is in a trivia gameshow or editing an encyclopedia. Although perhaps some jobs are indirectly like that, e.g. science fiction author

Boring though. But university researchers for example use a lot more than that. At least when I was in research for a time, I used probably 80% of what I learned, if not more. And now that I've gone independent, I use a lot more too because I enjoy it.

One of the main reasons why I quit was in fact intellectual boredom.