My home construction slipped 6 months on 2 year build time. It happens in construction very often.

> software is only tougher to estimate if incompetent people (vast majority of the industry, like 4+ million) is doing the estimating :)

No, it is tough to estimate, but not only for incompetent people. And "incompetent" can be stretched to "don't know what he's doing", which is how I operate most of the time. I don't know what really needs to be done until it's done. Main part of my work is research on what actually needs to be done, then "just" implementing it. If I waited with estimating until I know what needs to be done, I would spend 3/4 time estimating and then 1/4 with clear understanding and good schedules (example description: I will be clicking keys for 5 hours).