Plan­ning Fallacy

TagLast edit: 16 Nov 2009 20:25 UTC by Zack_M_Davis

A common cognitive bias resulting in predicting absurdly short timeframes for planned projects, famously observed with, among other projects, the Sydney Opera House, completed ten years late and a hundred million dollars overbudget.

Symptomatic of the Planning Fallacy is an assumption of a best-case scenario; people plan as if everything will go smoothly, as hoped for, with no unexpected delays. In practice, this is typically not the case, and delays quickly mount.

The bias also seems to be related to taking an “inside”, detail-oriented view of the project to be planned; studies show that the more detailed a plan is, the more optimistically inaccurate it is likely to be.

Debiasing techniques

When possible, take the outside view. Avoid estimating the time for a project by adding time estimates for sub-tasks; instead, look for previously completed projects of similar type and scale, and base the estimate on how long those other projects took.

Blog posts

See also

Chap­ter 6: The Plan­ning Fallacy

Eliezer Yudkowsky14 Mar 2015 19:00 UTC
63 points
5 comments32 min readLW link

Plan­ning Fallacy

Eliezer Yudkowsky17 Sep 2007 7:06 UTC
169 points
43 comments3 min readLW link

Kah­ne­man’s Plan­ning Anecdote

Eliezer Yudkowsky17 Sep 2007 16:39 UTC
37 points
8 comments2 min readLW link

Which cog­ni­tive bi­ases should we trust in?

Andy_McKenzie1 Jun 2012 6:37 UTC
29 points
42 comments3 min readLW link

A New Way to Vi­su­al­ize Biases

dtm22 Jul 2020 17:57 UTC
6 points
16 comments1 min readLW link

The Out­side View isn’t magic

Stuart_Armstrong27 Sep 2017 14:33 UTC
21 points
4 comments6 min readLW link

Sur­face Analo­gies and Deep Causes

Eliezer Yudkowsky22 Jun 2008 7:51 UTC
36 points
33 comments5 min readLW link

Fake Deeply

Zack_M_Davis26 Oct 2023 19:55 UTC
32 points
7 comments1 min readLW link

Plan­ning Fallacy

Eliezer Yudkowsky17 Sep 2007 7:06 UTC
169 points
43 comments3 min readLW link

Pri­vate Manned Moon­base in the 1990s, Yet Another Plan­ning Fallacy

DavidPlumpton5 Oct 2011 0:09 UTC
12 points
4 comments1 min readLW link

How to reach 80% of your goals. Ex­actly 80%.

Bart Bussmann10 Oct 2020 17:33 UTC
36 points
11 comments1 min readLW link
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