260:
32:
240:
optimistic. However, it is believed that forming implementation intentions "explicitly recruits willpower" by having the person commit themselves to the completion of the task. Those that had formed implementation intentions during the experiments began work on the task sooner, experienced fewer interruptions, and later predictions had reduced optimistic bias than those who had not. It was also found that the reduction in optimistic bias was mediated by the reduction in interruptions.
84:. The average estimate was 33.9 days. They also estimated how long it would take "if everything went as well as it possibly could" (averaging 27.4 days) and "if everything went as poorly as it possibly could" (averaging 48.6 days). The average actual completion time was 55.5 days, with about 30% of the students completing their thesis in the amount of time they predicted.
177:
the planner to deliberately underestimate the project effort required. It is easier to get forgiveness (for overruns) than permission (to commence the project if a realistic effort estimate were provided). Such deliberate underestimation has been named by Jones and Euske "strategic misrepresentation".
111:
Carter and colleagues conducted three studies in 2005 that demonstrate empirical support that the planning fallacy also affects predictions concerning group tasks. This research emphasizes the importance of how temporal frames and thoughts of successful completion contribute to the planning fallacy.
176:
The "authorization imperative" offers another possible explanation: much of project planning takes place in a context which requires financial approval to proceed with the project, and the planner often has a stake in getting the project approved. This dynamic may lead to a tendency on the part of
144:
Another explanation proposed by Roy and colleagues is that people do not correctly recall the amount of time that similar tasks in the past had taken to complete; instead people systematically underestimate the duration of those past events. Thus, a prediction about future event duration is biased
27:
and underestimate the time needed. This phenomenon sometimes occurs regardless of the individual's knowledge that past tasks of a similar nature have taken longer to complete than generally planned. The bias affects predictions only about one's own tasks. On the other hand, when outside observers
239:
are concrete plans that accurately show how, when, and where one will act. It has been shown through various experiments that implementation intentions help people become more aware of the overall task and see all possible outcomes. Initially, this actually causes predictions to become even more
227:
The segmentation effect is defined as the time allocated for a task being significantly smaller than the sum of the time allocated to individual smaller sub-tasks of that task. In a study performed by
Forsyth in 2008, this effect was tested to determine if it could be used to reduce the planning
102:
A survey of
Canadian tax payers, published in 1997, found that they mailed in their tax forms about a week later than they predicted. They had no misconceptions about their past record of getting forms mailed in, but expected that they would get it done more quickly next time. This illustrates a
136:
in how people interpret their past performance. By taking credit for tasks that went well but blaming delays on outside influences, people can discount past evidence of how long a task should take. One experiment found that when people made their predictions anonymously, they do not show the
54:
in 1979. In 2003, Lovallo and
Kahneman proposed an expanded definition as the tendency to underestimate the time, costs, and risks of future actions and at the same time overestimate the benefits of the same actions. According to this definition, the planning fallacy results in not only time
148:
Sanna and colleagues examined temporal framing and thinking about success as a contributor to the planning fallacy. They found that when people were induced to think about a deadline as distant (i.e., much time remaining) vs. rapidly approaching (i.e., little time remaining), they made more
197:, that as size of effort increases the error increases much more as a natural effect of inefficiencies of larger efforts' ability to react, particularly efforts that are not divisible in increments. Additionally this is contrasted with earlier efforts being more commonly on-time (e.g. the
212:
Bent
Flyvbjerg and Dan Gardner write that planning on government-funded projects is often rushed so that construction can begin as soon as possible to avoid later administrations undoing or cancelling the project. They say a longer planning period tends to result in faster and cheaper
310:
faced severe delay and a cost overrun. The construction started in 2005 and was expected to be completed by 2009, but completed only in 2023. Initially, the estimated cost of the project was around 3 billion euros, but the cost has escalated to approximately 10 billion euros.
209:) to conclude it indicates inherent flaws in more modern planning systems and modern efforts having hidden fragility. (For example, that modern efforts – being computerized and less localized invisibly – have less insight and control, and more dependencies on transportation.)
303:
is another case. After 15 years of planning, construction began in 2006, with the opening planned for
October 2011. There were numerous delays. It was finally opened on October 31, 2020. The original budget was €2.83 billion; current projections are close to €10.0 billion.
87:
Another study asked students to estimate when they would complete their personal academic projects. Specifically, the researchers asked for estimated times by which the students thought it was 50%, 75%, and 99% probable their personal projects would be done.
192:
issues. The asymmetry results from random events giving negative results of delay or cost, not evenly balanced between positive and negative results. The scaling difficulties relate to the observation that consequences of disruptions are not
28:
predict task completion times, they tend to exhibit a pessimistic bias, overestimating the time needed. The planning fallacy involves estimates of task completion times more optimistic than those encountered in similar projects in the past.
228:
fallacy. In three experiments, the segmentation effect was shown to be influential. However, the segmentation effect demands a great deal of cognitive resources and is not very feasible to use in everyday situations.
495:
Buehler, Roger; Griffin, Dale, & Ross, Michael (2002). "Inside the planning fallacy: The causes and consequences of optimistic time predictions". In Thomas
Gilovich, Dale Griffin, & Daniel Kahneman (Eds.),
121:
Kahneman and
Tversky originally explained the fallacy by envisaging that planners focus on the most optimistic scenario for the task, rather than using their full experience of how much time similar tasks
271:
was expected to be completed in 1963. A scaled-down version opened in 1973, a decade later. The original cost was estimated at $ 7 million, but its delayed completion led to a cost of $ 102 million.
1070:
156:, proposes that people fall victim to the planning fallacy because they only focus on the future task and do not consider similar tasks of the past that took longer to complete than expected.
441:
552:
Pezzo, Mark V.; Litman, Jordan A.; Pezzo, Stephanie P. (2006). "On the distinction between yuppies and hippies: Individual differences in prediction biases for planning future tasks".
103:
defining feature of the planning fallacy: that people recognize that their past predictions have been over-optimistic, while insisting that their current predictions are realistic.
789:
Sanna, Lawrence J.; Parks, Craig D.; Chang, Edward C.; Carter, Seth E. (2005). "The
Hourglass Is Half Full or Half Empty: Temporal Framing and the Group Planning Fallacy".
317:
is still under construction, with tens of billions of dollars in overruns expected, and connections to major cities postponed until after completion of the rural segment.
137:
optimistic bias. This suggests that the people make optimistic estimates so as to create a favorable impression with others, which is similar to the concepts outlined in
843:
Roy, Michael M.; Christenfeld, Nicholas J. S.; McKenzie, Craig R. M. (2005). "Underestimating the
Duration of Future Events: Memory Incorrectly Used or Memory Bias?".
149:
optimistic predictions and had more thoughts of success. In their final study, they found that the ease of generating thoughts also caused more optimistic predictions.
145:
because memory of past event duration is also biased. Roy and colleagues note that this memory bias does not rule out other mechanisms of the planning fallacy.
1151:
1078:
626:
Kahneman, Daniel; Tversky, Amos (1982). "Intuitive prediction: Biases and corrective procedures". In
Kahneman, Daniel; Slovic, Paul; Tversky, Amos (eds.).
1126:
474:
169:, adding new personnel to an already-late project incurs a variety of risks and overhead costs that tend to make it even later; this is known as
1176:
1043:
1252:
990:
975:
816:
Pezzo, Stephanie P.; Pezzo, Mark V.; Stone, Eric R. (2006). "The social implications of planning: How public predictions bias future plans".
375:
Buehler, Roger; Dale Griffin; Michael Ross (1994). "Exploring the "planning fallacy": Why people underestimate their task completion times".
442:"Overcoming the planning fallacy through willpower: Effects of implementation intentions on actual and predicted task-completion times"
1232:
1213:
643:
324:
went over budget by approximately 9 billion dollars, and was sent into orbit 14 years later than its originally planned launch date.
740:
460:
410:
Kruger, Justin; Evans, Matt (15 October 2003). "If you don't want to be late, enumerate: Unpacking Reduces the Planning Fallacy".
251:
predicts the outcome of a planned action based on actual outcomes in a reference class of similar actions to that being forecast.
595:
928:
688:
307:
259:
293:
129:; in other words, people think tasks will be finished quickly and easily because that is what they want to be the case.
1100:
248:
719:
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opened sixteen months later than scheduled, with a total cost of $ 4.8 billion, over $ 2 billion more than expected.
321:
314:
300:
289:
was completed seven years later than planned, for $ 8.08 billion on a budget of $ 2.8 billion (in 1988 dollars).
1272:
1267:
520:
Buehler, Roger; Dale Griffin; Michael Ross (1995). "It's about time: Optimistic predictions in work and love".
236:
23:
is a phenomenon in which predictions about how much time will be needed to complete a future task display an
31:
852:
165:
180:
Apart from psychological explanations, the phenomenon of the planning fallacy has also been explained by
606:
339:
198:
181:
138:
888:
Wilson, Timothy D.; Wheatley, Thalia; Meyers, Jonathan M.; Gilbert, Daniel T.; Axsom, Danny (2000).
857:
263:
Sydney Opera House, still under construction in 1966, three years after its expected completion date
1047:
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defense project took six years longer than expected, with an overrun cost of 8 billion euros.
133:
60:
92:
13% of subjects finished their project by the time they had assigned a 50% probability level;
1015:
901:
862:
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798:
728:
631:
561:
529:
501:
464:
456:
419:
384:
126:
1004:"Allocating time to future tasks: The effect of task segmentation on planning fallacy bias"
768:
673:
619:
47:
35:
170:
1044:"No Light at the End of his Tunnel: Boston's Central Artery/Third Harbor Tunnel Project"
588:
286:
732:
1261:
333:
189:
81:
56:
24:
889:
132:
In a different paper, Buehler and colleagues suggest an explanation in terms of the
396:
51:
39:
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160:
905:
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423:
388:
802:
533:
77:
573:
342: – How ignorance intersects with rational choice to undertake a project
185:
1127:"Finland starts much-delayed nuclear plant, brings respite to power market"
1029:
913:
874:
704:
653:
153:
1152:"After 18 years, Europe's largest nuclear reactor starts regular output"
1020:
1003:
461:
10.1002/1099-0992(200011/12)30:6<873::AID-EJSP22>3.0.CO;2-U
282:
80:
students were asked to estimate how long it would take to finish their
469:
689:"Delusions of Success: How Optimism Undermines Executives' Decisions"
194:
1046:. Project on Government Oversight. 1 February 1995. Archived from
258:
125:
Roger Buehler and colleagues account for the fallacy by examining
30:
721:
The Planning Fallacy: Cognitive, Motivational, and Social Origins
336: – Risk of the actual return being below the expected return
890:"Focalism: A source of durability bias in affective forecasting"
991:
For infrastructure projects to succeed, think slow and act fast
1204:
Bent Flyvbjerg; Nils Bruzelius; Werner Rothengatter (2003).
1177:"Finland's Olkiluoto 3 nuclear reactor faces another delay"
498:
Heuristics and biases: The psychology of intuitive judgment
500:, pp. 250–270. Cambridge, UK: Cambridge University Press.
354: – Adage that work expands to fill its available time
348: – Self-referential adage referring to time estimates
95:
19% finished by the time assigned a 75% probability level;
1106:. United States General Accounting Office. September 1995
589:"Intuitive prediction: Biases and corrective procedures"
98:
45% finished by the time of their 99% probability level.
1071:"Governor seeks to take control of Big Dig inspections"
624:
Decision Research Technical Report PTR-1042-77-6. In
933:
Journal of Public Administration Research and Theory
718:
Buehler, Roger; Dale Griffin; Johanna Peetz (2010).
370:
368:
963:
927:Jones, Larry R; Euske, Kenneth J (October 1991).
628:Judgment Under Uncertainty: Heuristics and Biases
547:
545:
543:
791:Group Dynamics: Theory, Research, and Practice
491:
489:
487:
1225:The Oxford Handbook of Megaproject Management
1206:Megaprojects and Risk: An Anatomy of Ambition
784:
782:
780:
778:
440:Koole, Sander; Van't Spijker, Mascha (2000).
16:Cognitive bias of underestimating time needed
8:
894:Journal of Personality and Social Psychology
687:Lovallo, Dan; Kahneman, Daniel (July 2003).
377:Journal of Personality and Social Psychology
966:Antifragile: Things That Gain from Disorder
515:
513:
46:The planning fallacy was first proposed by
929:"Strategic misrepresentation in budgeting"
1247:, Vienna, VA: Management Concepts, 2008.
1019:
856:
818:Journal of Experimental Social Psychology
468:
412:Journal of Experimental Social Psychology
587:Kahneman, Daniel; Tversky, Amos (1977).
601:from the original on September 8, 2013.
364:
1244:Project Decisions: The Art and Science
1125:Lehto, Essi; Buli, Nora (2022-03-16).
764:
754:
669:
659:
615:
604:
554:Personality and Individual Differences
449:European Journal of Social Psychology
7:
522:European Review of Social Psychology
435:
433:
308:Olkiluoto Nuclear Power Plant Unit 3
630:. Vol. 185. pp. 414–421.
14:
1241:Lev Virine and Michael Trumper.
1069:Johnson, Glen (July 13, 2006).
727:. Vol. 43. pp. 1–62.
1208:. Cambridge University Press.
1101:"Denver International Airport"
1:
733:10.1016/s0065-2601(10)43001-4
1223:Bent Flyvbjerg, ed. (2019).
1002:Forsyth, D. K. (June 2008).
939:(4): 437–460. Archived from
636:10.1017/CBO9780511809477.031
506:10.1017/CBO9780511808098.016
294:Denver International Airport
1227:. Oxford University Press.
970:. Random House Publishing.
867:10.1037/0033-2909.131.5.738
249:Reference class forecasting
244:Reference class forecasting
1294:
1150:Lehto, Essi (2023-04-15).
906:10.1037/0022-3514.78.5.821
830:10.1016/j.jesp.2005.03.001
566:10.1016/j.paid.2006.03.029
424:10.1016/j.jesp.2003.11.001
389:10.1037/0022-3514.67.3.366
322:James Webb Space Telescope
315:California High-Speed Rail
301:Berlin Brandenburg Airport
184:as resulting from natural
1175:Buli, Nora (2021-08-23).
803:10.1037/1089-2699.9.3.173
534:10.1080/14792779343000112
237:Implementation intentions
232:Implementation intentions
218:Methods for counteracting
285:which undergrounded the
693:Harvard Business Review
1008:Memory & Cognition
962:Taleb, Nassim (2012).
845:Psychological Bulletin
614:Cite journal requires
264:
166:The Mythical Man-Month
43:
42:, proposed the fallacy
340:Hiding hand principle
287:Boston Central Artery
262:
199:Empire State Building
139:impression management
116:Proposed explanations
34:
76:In a 1994 study, 37
72:For individual tasks
1021:10.3758/MC.36.4.791
276:Eurofighter Typhoon
255:Real-world examples
223:Segmentation effect
55:overruns, but also
1050:on 8 November 2014
269:Sydney Opera House
265:
207:Golden Gate Bridge
203:The Crystal Palace
67:Empirical evidence
61:benefit shortfalls
44:
1253:978-1-56726-217-9
1081:on March 11, 2007
977:978-1-4000-6782-4
152:One explanation,
134:self-serving bias
1285:
1273:Cognitive biases
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1077:. Archived from
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999:
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560:(7): 1359–1371.
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517:
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481:
479:
473:. Archived from
472:
446:
437:
428:
427:
407:
401:
400:
372:
346:Hofstadter's law
159:As described by
127:wishful thinking
38:who, along with
21:planning fallacy
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1292:
1288:
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1286:
1284:
1283:
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1268:Prospect theory
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1198:Further reading
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107:For group tasks
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48:Daniel Kahneman
36:Daniel Kahneman
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1014:(4): 791–798.
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900:(5): 821–836.
880:
851:(5): 738–756.
835:
824:(2): 221–227.
808:
797:(3): 173–188.
774:
765:|journal=
741:
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670:|journal=
645:978-0511809477
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616:|journal=
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483:
480:on 2019-11-29.
455:(6): 873–888.
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418:(5): 586–598.
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383:(3): 366–381.
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57:cost overruns
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25:optimism bias
22:
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1184:. Retrieved
1180:
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1159:. Retrieved
1155:
1145:
1134:. Retrieved
1130:
1120:
1108:. Retrieved
1095:
1083:. Retrieved
1079:the original
1075:Boston Globe
1074:
1064:
1052:. Retrieved
1048:the original
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1007:
997:
986:
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945:. Retrieved
941:the original
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746:. Retrieved
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699:(7): 56–63.
696:
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607:cite journal
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475:the original
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1262:Categories
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748:2012-09-15
470:1871/17588
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188:and from
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