

Why are software development task estimations regularly off? - andreasklinger
http://www.quora.com/Engineering-Management/Why-are-software-development-task-estimations-regularly-off-by-a-factor-of-2-3/answer/Michael-Wolfe?srid=24b&share=1

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a3n
The fundamental reason is that we start with a fallacy, that you can predict
with any accuracy how long it will take to build a complex and likely poorly
specified system in its entirety.

On top of that, there are two common development environments. In the
enlightened one, management asks you or your team to go off and create an
estimate. You come back and tell it to them, and you're informed that it's
crucial to deliver to an important customer by date N. So you go back to your
desks, lie to yourselves, then come back and tell management that you've
recast the problem a bit and you can bring it in by the required date. Then
you either blow the date, or deliver garbage by the date.

The more common environment, management either baldly states or subtly
telegraphs the required date. You go back to your desks, then come back to
management and show them the estimate, which will be done by the required
date. Then you either blow the date, or deliver garbage by the date.

I've heard that some people don't do it that way.

