The article is really cool even though it is a little bit simplistic in my view (and experience). I've also made this comment on the article by the way. The fir

The article is really cool even though it is a little bit simplistic in my view (and experience). I've also made this comment on the article by the way. The first problem is that rarely steps are independent from each other. I haven't seen hard data on this (and if they have hard data, they should look at it) but my guess is that if one step fell behind schedule, there's an higher probability for the next step to fall behind schedule. That's because the reason a step is behind schedule is not purely random but depends on the internal element of the project (it is harder than usual, using new tech, a person is overloaded and always late...) and all this problem will not magically disappear in the next steps. The second issue is that project are not so simple as a sequence of task. They usually have tasks in parallel,with different dependencies and sync point. Accounting for time variations on each step quickly become a total mess.