Why do estimation always wrong?

It's been asked by every boss or project manager. Everyone got their own version but mine is always like,

- too religious towards the end date
- over estimate the efficiency
- a tendency to accept excessive risks

When a new project started, the first thing being asked (or told) is, "When could it complete?'" or "We must finish by bla bla bla.".

In the first scenario, even though the end date is not pre-defined but the project owner usually already got something in mind. Thus, the end date looks flexible but not really that flexible. Whenever the team comes back with a date later then his desire, the usual and only response is "Finding more people to do it"!

Instead of spending time to discuss on what the risk are, "solutions" are being put forward right away. The outcome? Pitfall is being skimmed through.

Another common management principal is, parallelism. Can we work in parallel? Could a task breaks further down? It could work, but only if the team is well balanced. When the project demands a particular skillset which only a single entity can fulfill, asking him to context switch and leverage the resources will not shorten the development time. Also, there's an overhead on communication, which if not managed properly, can result in tasks undone.

When we do estimation, we are always ignoring the fact that we are not as efficient as we want to be. Able to spend 70% on the project is already very efficient. Take myself as an example, I am spending 50% of my time helping to team to resolve projects issues, 20% on daily matters (like development and operation daily issues). But I am still assigning tasks to myself which leaves out to at most 30% of my available time.

Are there solutions? There is, but takes time to practice, which I am still working hard on.

Be persistent. Don't give it up or rush out for a decisoin even when we are pressed. There are not as many "life-or-death" issues. When we need to labor a baby, there's no short cut but 9 months of pregnancy.

Be realistic. If we can only afford 30% of work hours, stick with that. Don't try to fool yourself, or your project manager that the week after will be better.

I don't know about you but to me, family and health is more important than work. Save your late night and weekend, you've got a life project to fulfill which don't stand a second chance.