I suspect that 20% is underestimation. And this makes me wonder what sort of mistakes you’re usually doing since they cannot be detected with type checks — or possibly you take the help from IDE and compiler for granted when you write typed code (is there such thing as five-second rule in programming?). I guess, YMMV, depending on what languag…
When I program in Smalltalk, a dynamically-typed language, I very seldom make type-related errors, that is to say, I very seldom make errors that could be caught in a statically-typed language. (I make many other kinds of errors.)
I can compare this experience with C programming, which I did throughout my 20-year career as a software engineer. (I’ve only done Smalltalk programming since retirement.)
In other words, I’ve worked on both sides of the fence and the kind of data typing I use is completely irrelevant.
Thus, I don’t buy the crap about type-related errors that cannot be detected with type checks.