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.<p>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.