“It’s not surprising, therefore, that projects tended to be behind schedule. Take a plan that’s created according to a generic formula, estimate the work in advance of any significant knowledge of requirements, have the estimates done by people who won’t be doing the work, never update the plan after work is started, and what do you get? Lousy plans… and they were treated as unquestionable truths.”

http://jamesshore.com/Change-Diary/