I'm not sure how I'd even go about tracking such a stat. It might take me 10 minutes to code something, but I'll often be thinking about it off and on to come up with solutions at all hours of the day. Plus, I maintain I don't know how many plugins/themes. Sometimes, 3 hours of work for one project will result in 5 minutes of work on another project that uses some of the same code. I also often jump from project to project while I'm working. I don't see it as a realistic stat I could track.