I think most knowledge workers only have 4 hours of productive work a day, if you don't count screwing off on facebook or hn or what have you. 30 hours, I thin

I think most knowledge workers only have 4 hours of productive work a day, if you don't count screwing off on facebook or hn or what have you. 30 hours, I think, is a good expectation of a salary worker, assuming they work for most of those 30 hours.