What academic discipline does "Productivity Science" come under? I wish to categorise my large collection of electronic documents. I need a foolproof set of categories to put each document in. I want to use a classification system similar to how university schools are organized:

http://en.wikipedia.org/wiki/List_of_academic_disciplines

Some of my documents are productivity tips (similar to Dave Allen's "Getting Things Done" book). I can't find an academic category under which productivity comes. The term "productivity science" doesn't seem to be a widely accepted term.

What is the most natural category to put the study of "Productivity" in? Psychological Sciences (or other Social Sciences)? Applied Sciences/Professions? I'm tempted to put it in Psychology because I have other documents based on Learning, Memory and Performance. The four of those seem best suited to Psychological Sciences.
There is no such thing as a


  a foolproof set of categories to put each document in


With paper documents the document had to "live" in a single locations and therefore needed a primary category/label/tag. You then had lots of different indexes that would allow you to find the document from multiple places. You often had to walk to a different library to collect the document. This system was/is inefficient and problematic.

Electronic documents can "live" in multiple places. The concept of assigning a single primary category to an electronic document is dated and silly. You should either modify the file directly to add helpful metadata or create a database that lets you externally create searchable metadata. This then allows you to easily search for the document, and related documents.