Project timelines slip.

Whether it’s a construction plan, a large report that needs to be completed, or a team development project; it’s fairly safe to say that a project won’t be delivered on time.

Even when we try to be conservative, we still underestimate timelines.

Why?

There are several contributing factors including our inability to accurately anticipate every task that needs to be completed and our inherent optimism.

But the most important factor is the asymmetry in the effects of positive and negative events.

Take driving as an example.

If it usually takes 30 minutes to drive to work, sometimes it will take more time and sometimes it will take less time. Realistically, the absolute fastest you’d probably make it to work in a given day is 27 or 28 minutes.

There’s a limit to how much time you can save without driving absurd speeds and ignoring traffic laws.

But the potential impact on the other side is unbounded.

It isn’t unrealistic to assume that sometimes it will take 35, 40, or even 50 minutes to get to work. Bad weather, construction, or an accident can easily add significant time to your commute.

Going back to project timelines, the impact is very similar.

If a given task goes perfectly smoothly, you’ll probably save 5%/10% of the task timeline. But if things go wrong, you can easily add 50%, or even several times the timeline as you try to correct the error.

Thus, if we use the average time for each task to calculate the overall project timeline, we’ll be short almost every time.

-Brandon