This legit happened to a college of mine, at his first job (as engineer), it took me well into his second year of employment (the time when he got the second yearly income tax stats) to get him to understand what I've been explaining to him since he was offered a raise a few months after he started.

I tried, I really did, with charts, examples, my own income tax statement, ... but no.

I never found out which part was bothering him, like theoretically, how tf ...