On your quiz, the average answer is "3-5 hours," and this squares with recent research suggesting that in an 8-hour day, mind workers are doing actual work about 3 1/2 hours on average. The rest of the day is spent on snacking, gossiping, Facebook, etc. I'm a highly motivated independent developer and writer, and I've been studying my own work habits to try to become more productive. I use toggl — https://www.toggl.c…
I spent some time with google looking for the references to no avail, but from what I recall, the SEI (Software Engineering Institute) agrees with you. Measured across thousands of projects, the average number of hours of actual software development is 2-4 hours per day.
In my experience with teams actively and accurately tracking time, the average is about 2.5 hours for most development work. It can spike up, but the spikes are typically not sustainable for more than a few days. Even then, the higher number days are typically spent doing design documentation or other non-coding tasks.