The missing categories

I finally got around to creating a spreadsheet of all the of unassigned or optional categories. Unassigned categories are ones that have been moved, deleted, or were never in use. Optional are categories where the official standard allows "options to standard practice", whatever that means. Almost all of the optional categories are under 920 Biography, so perhaps some libraries used those values to organize biographies?

Here is a summary table of all the missing categories:

Unassigned categories