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Plan­ning Fallacy

TagLast edit: Oct 2, 2020, 12:29 AM by Ruby

The Planing Fallacy is 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 YudkowskyMar 14, 2015, 7:00 PM
72 points
7 comments32 min readLW link

Plan­ning Fallacy

Eliezer YudkowskySep 17, 2007, 7:06 AM
185 points
43 comments3 min readLW link

Kah­ne­man’s Plan­ning Anecdote

Eliezer YudkowskySep 17, 2007, 4:39 PM
38 points
8 comments2 min readLW link

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

DavidPlumptonOct 5, 2011, 12:09 AM
12 points
4 comments1 min readLW link

A New Way to Vi­su­al­ize Biases

dtmJul 22, 2020, 5:57 PM
6 points
16 comments1 min readLW link

The Out­side View isn’t magic

Stuart_ArmstrongSep 27, 2017, 2:33 PM
21 points
4 comments6 min readLW link

Sur­face Analo­gies and Deep Causes

Eliezer YudkowskyJun 22, 2008, 7:51 AM
38 points
33 comments5 min readLW link

Which cog­ni­tive bi­ases should we trust in?

Andy_McKenzieJun 1, 2012, 6:37 AM
29 points
42 comments3 min readLW link

Fake Deeply

Zack_M_DavisOct 26, 2023, 7:55 PM
33 points
7 comments1 min readLW link
(unremediatedgender.space)

Plan­ning Fallacy

Eliezer YudkowskySep 17, 2007, 7:06 AM
185 points
43 comments3 min readLW link

Strong-Misal­ign­ment: Does Yud­kowsky (or Chris­ti­ano, or TurnTrout, or Wolfram, or…etc.) Have an Ele­va­tor Speech I’m Miss­ing?

Benjamin BourlierMar 15, 2024, 11:17 PM
−4 points
3 comments16 min readLW link

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

Bart BussmannOct 10, 2020, 5:33 PM
36 points
11 comments1 min readLW link
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