[brissmyr]

I agree to some extent. My hypothesis is that during a project you take a lot of shortcuts, because solving that last part of a task sometimes involves a lot of work to get everything perfect and working for every user. It could be making a responsive website work in legacy browsers, or it could be a script I know works in my dev environment but I haven't yet tested in production,. Even so I close my eyes, mark these task as done and move along.

So the last 20% is actually a bunch of 0.5 percenters pushed to the end of a project. At least for me.