Reminds me of Hofstadter's Law: It always takes longer than you think, even when you take into account Hofstadter's Law.

We could say, always say it will take longer than you think?

Though by this principle, it seems that "overestimates" are likely to be actually accurate?

Joel Spolsky wrote about his time estimation software which recorded the actual time required for completion, and then calculated for each person a factor by which their estimates were off, and this factor was consistent enough that it could be reliably used as a multiplier to improve estimation accuracy.

> Most estimators get the scale wrong but the relative estimates right. Everything takes longer than expected, because the estimate didn’t account for bug fixing, committee meetings, coffee breaks, and that crazy boss who interrupts all the time. This common estimator has very consistent velocities, but they’re below 1.0. For example, {0.6, 0.5, 0.6, 0.6, 0.5, 0.6, 0.7, 0.6}

https://www.joelonsoftware.com/2007/10/26/evidence-based-sch...

Doesn't the article say that for experienced developers, the scaling factor tended to be converge on an average for each individual, even if variable for any particular task?

And Joel sidesteps the unknown-unknowns problem in that piece, by discussing boiling down tasks to <1 day chunks.

But what if you need to build a prototype before you sufficiently understand the project and options to decide on an approach? Where does that time get estimated?

The more projects I work on, the bigger of a fan of spiral development [0] I become.

Because, at root, there are 2 independent variables that drive project scheduling -- remaining work and remaining risk.

This estimation problem would drastically simplify if it allowed for "high confidence, 30 days" and "low confidence, 5 days" estimates.

And critically, that could drive different development behavior! E.g. prototype out that unknown feature where most of the remaining technical risk is.

Trying to instead boil that down to an un-risk-quantified number produces all the weird behaviors we see discussed elsewhere in the comments.

[0] https://en.m.wikipedia.org/wiki/Spiral_model

I’m more of a Parkinson’s Law person: "Work expands so as to fill the time available for its completion.”

Things take longer but if you over-estimate the project won’t come in significantly any earlier.