[ghaff]

Right. Even if I, say, spend half the day taking a walk, vaguely mulling some task in background, doing some vaguely related reading, chatting with colleagues etc. doesn't mean I'd get as much work done if my hours were 9-1. Would I get more than 50% of my work done? Probably. But I'm pretty sure it wouldn't be 100%.

I actually think if I took every Friday off, I could probably hit pretty close to current productivity but I work a pretty flexible schedule and don't have to do a lot of coordination.