Time for PlanningYou’re planning how long a project will take you, so you can set a realistic deadline. If you’re like most of us, you take an “educated guess”, but your guess will fall victim to the Planning Fallacy, because you use the best case scenario about:

  • The amount of time the project will take overall
  • The effect of interruptions and disruptions
  • The impact of illness, holidays, bad hair days
  • The time available to you
  • Conflicts with your other commitments
  • Dependencies you hadn’t considered, like other people

And even if you know about the planning fallacy, it’s hard to cancel out the rosy view and override the “can do” attitude. There is a rich vein of stories about the effect of such blunders. We hear of many public works projects, where the plan had a completion deadline of 12 months, but an achieved completion of 36 months. The FIFA World Cup in Rio this year was bedevilled with late-running and half built stadia. It’s still touch and go.

My personal favourite is a story by Daniel Kahnemann, he won the Nobel prize for Economics for his work on decision-making and, together with Amos Tversky, coined the term Planning Falllacy. But even he fell victim to it. In his book, “Thinking Fast and Slow” he describes the most embarrassing and informative professional mistake of his life. He was designing a text book – about decision making, together with some colleagues. Following a procedure which was outlined in the book to improve the quality of decision making, he  polled his colleagues individually, asking them how long it would take to write the text book. This approach is more effective than reaching a group consensus. The low end estimate was one and a half years, the high end was two and a half. Then Kahnemann asked  the curriculum expert in the team (who had just voted two years) about similar projects with the same context. The answer surprised everybody, including the expert himself,  because when he actually thought about it, 40% of the projects he could think of had never actually finished. The ones that did finish took 7 years or more. 


“After a few minutes of desultory debate, we gathered ourselves together and carried on as if nothing had happened. The book was eventually completed eight years later”

And it was never used.

So how can you correct for the planning fallacy? There are two things to think about: Task Duration – the time it would take if you had a clear, continuous run at it, with no break. And Elapsed Time, the overall time it will take when you take your life into account.

Kahnemann recommended taking an outside view, by consulting the statistics of similar cases – it’s called reference class forecasting. How long has a project like this taken other people in the past? It’s better if you don’t use your own hazy recollections as a reference. Try using an independent third-party, or a disinterested friend.

Another approach to calculate a realistic Task Duration is to divide it up into smaller, concrete steps, that you can visualise yourself doing. This anchors you into reality, and out of wishful thinking, so you have a series of milestones that you can plan with and check progress against. It’s the same technique I used for coaching Marathon runners. Say I decide my task will take 4 hours in total.

Then have a look at your diary. The chances are there’s more in it over the next couple of weeks than there is further out in the future. You’re not really going to have more free time in the future, though. It just means you haven’t filled your diary up yet. So imagine that you’re going to start right now, today. Take the smaller concrete steps and plan them into the free slots in your diary as it is today. You should end up with something like this:


My four hours is now spread out into what free time I have. I can see that in Elapsed Time, my four-hour project is going to take me five days! You can use that 5 days as an estimate, regardless of what the start date actually is. You’ve used your diary for this week to plan a task for any time in the future.

Give it a try.
 Find Out More