Fuzzy Grading

This is probably boring to anyone who came here expecting analysis of major social injustices and environmental problems, but it's also inevitable that academics will eventually discuss pedagogy.

I've recently encountered some discussion about the relative merits of different types of grading scales, particularly on the question of grading scales with lots of places (e.g. 0-100% or letter grades with pluses and minuses) versus those with few places (e.g. letter grades without pluses and minuses, or check plus/check minus).

Insofar as the people involved are willing to discuss the relative merits of grading systems (rather than rejecting the whole idea of grading), they seem to agree that scales with fewer places are better. The rationale is that grading is a highly inexact process -- but having lots of places on the scale presumes an unrealistic ability to discriminate between, say, 85% and 86%-quality work.

In my opinion, the inexactness of grading cuts the other way. If you only have a few scale places to work with, your decisions about borderline cases take on heightened importance, since the difference between the grades on either side of the border is so much larger. How can I be certain that all the papers I gave Bs to are definitely better than all the ones I gave Cs, given the inexactness of grading? But if I have more places on the scale, I can give a B- or a C+ to those borderline students, acknowledging the fuzziness of the categories and the uncertainty inherent in grading.