I had a thought today. The amount of work you can do in an hour is mostly determined by the difficulty of the work. If it's hard you'll get a little done, if it's easy you'll get a lot done.
Obvious. How much work can you do in a week, then? I say that it has very little to do with the difficulty of the work, and everything to do with how motivated you are.
Don't believe me? How often have you had a really easy task like ebaying a pile of aging computing parts drag out over weeks, months, or even years? On the flip side, have you ever been so excited about your work that it seemed like you did the work of ten people?
If I were an employer, I would spend little energy worrying about how many hours my employees were working, and lots of energy making sure they were motivated by the work.
As a self employed person, I make sure I do projects I'm interested in.