Planning error

Concerning personal tasks

In a 1994 study, 37 psychology students were asked to estimate how long it would take to finish their graduate work . The average score was 33.9 days. They also estimated how long it would take, “if everything goes best” (27.4 days on average) and “if everything goes best” (48.6 days on average). The average actual time for completion of the work was 55.5 days; only about 30% of students completed their work in the time that they predicted. ^[9]

In another study, students were asked to evaluate when they would finish their personal academic projects. In particular, the researchers asked students to rate the time taken to complete their project with a 50%, 75%, and 99% probability. ^[7]

• 13% of subjects completed their project in a time to which they gave 50% probability;
• 19% for the time given 75% probability;
• 45% for the time given 99% probability.

A 1997 Canadian taxpayer survey revealed that they filed their tax returns a week later on average than they predicted. The taxpayers knew very well at what time they filed returns in previous years, but thought that this time they would do it faster. ^[10] This illustrates a key point in the planning error: people admit that their past forecasts were overly optimistic, but each time they insist that their current forecasts are realistic. ^[6]

In relation to collective tasks

Carter and his colleagues conducted three studies in 2005, which empirically confirm that planning errors also affect group tasks. These studies emphasize the importance of how time frames ( frames ) and the mood for successful tasks lead to planning errors. ^[eleven]

Additional research

Bent Flyvbjerg and Cass Sunstein argue that Albert Hirschman ’s “hiding hand principle” describes gross planning errors, and they tested the empirical validity of this principle. ^[12]

• Kahneman and Tversky initially explained this distortion by the fact that the designers focus on the most optimistic scenario, rather than fully utilizing the experience of performing similar tasks ^[6] .
• Roger Buhler and colleagues analyze this fallacy on the basis of wishful thinking ; in other words, people think that the task will be completed quickly and easily, because this is what they want ^[1] .
• In another article, Buhler and colleagues offer an explanation from the point of view of selfish bias in how people interpret their past performance. Relating past successes to their own account, and failures to the influence of external factors, people can distort their vision of the upcoming task ^[1] . In one experiment, it was found that when people make their predictions anonymously, they are not prone to excessive optimism. This suggests that people make optimistic assessments in order to create a favorable impression for other people ^[13] . Here the study of planning errors is at the junction with the study of self-presentation .
• Another explanation proposed by Roy and colleagues is that people incorrectly remember the amount of time it took for similar tasks in the past ^[14] .
• Studies conducted by Sanna and his colleagues indicate that the planner team, focusing on the thought of successful completion of the task, makes more optimistic forecasts for it ^[11] .
• The explanation based on the binding effect suggests that people become victims of planning errors because they focus only on the future task in the planning process and do not take into account the experience of solving past problems ^[15] .
• Fred Brooks in his Mythical Man-Month showed that adding new employees at the end of a protracted project entails additional risks and overhead and, as a rule, leads to an additional delay and higher cost of the project (“Brooks law”).
• The “imperative of approval” offers another possible explanation: most of the project planning takes place in a situation in which you need to obtain permission to finance the project, and since the planner is often interested in obtaining such permission, he is inclined to consciously underestimate the assessment of necessary efforts. It is easier to get forgiveness (in case of an overrun) than approval (to start the project, if you really appreciate the effort). Jones and Yuske called such deliberate underestimation "strategic distortion" ^[16] .
• Without resorting to psychological explanations, Taleb considers planning errors as a consequence of natural asymmetry and scaling problems. Asymmetry occurs if a disproportionate amount of random events occurs during the solution of a problem, causing delays or additional costs. The problem of scaling is connected with the fact that the consequences of negative events are not linear: negative events have the greater impact, the more complex the project, since in a more complex project it is more difficult to deal with their consequences. Moreover, the fact that earlier projects were better planned (for example, the Empire State Building , the Crystal Palace , the Golden Gate Bridge ) indicates the flaws ("fragility") inherent in modern planning systems. Modern projects, being computerized and less localized, are less susceptible to understanding and control by people, and are more dependent on transport ^[17] .

Segmentation Effect

One aspect of the planning error is that the time allocated to the task as a whole is significantly less than the sum of the time allocated to its individual smaller sub-tasks. In a study conducted by Foresight in 2008, a segmentation effect was proposed to overcome errors in planning complex tasks. Three experiments have shown that the segmentation effect has a positive effect. However, the segmentation effect requires a lot of cognitive resources and it is not very advisable to use it in everyday situations ^[18] .

Implementation Plans

Implementation plans are specific plans for how, when, and where to act. Through various experiments, it was shown that implementation plans help people plan the task as a whole and provide for all possible scenarios. At the first stage, the development of implementation plans leads to forecasts becoming even more optimistic. However, it is believed that implementation planning encourages a person to assume obligations to complete the task and thereby mobilizes his volitional qualities. Those experiment participants who developed implementation plans started working on the task earlier, experienced fewer interruptions, and their forecasts subsequently reduced their optimistic bias. It was also found that reducing interruptions in the task led to a decrease in optimistic bias ^[5] .

Analog Prediction

Forecasting by analogs is based on a correct quantitative analysis of the actual results of past actions similar to those planned.

Sydney Opera House was due to be completed in 1963. It was eventually opened in 1973, a decade later, and in a simplified version. Initially, the cost was estimated at $ 7 million, but its untimely completion increased the actual cost to $ 102 million ^[11] .

The defense project Eurofighter Typhoon took six years longer than expected, with an excess of 8 billion euros over the planned cost ^[11] .

was completed seven years later than planned and with a cost overrun of $ 12 billion. ^[19]

Denver International Airport was opened sixteen months later than planned and cost $ 4.8 billion, more than $ 2 billion more than expected ^[20] .

• The principle of the hiding hand (English)
• Hofsteder's Law
• Parkinson's law

• Lev Virine and Michael Trumper. Project Decisions: The Art and Science , Vienna, VA: Management Concepts, 2008. ISBN 978-1-56726-217-9
• The Planning Fallacy by Roger Buehler
• Chapter One - The Planning Fallacy: Cognitive, Motivational, and Social Origins by Roger Buehler, Dale Griffin, and Johanna Peetz
• If you don't want to be late, enumerate: Unpacking reduces the planning fallacy by Matt Evans and Justin Kruger
• Overcoming the planning fallacy through willpower: effects of implementation intentions on actual and predicted task-completion times by Sander Koole
• The Hourglass Is Half Full or Half Empty: Temporal Framing and the Group Planning Fallacy by Seth Carter, Edward Chang, Craig Parks, and Lawrence Sanna
• Underestimating the Duration of Future Events: Memory Incorrectly Used or Memory Bias? by Nicholas Christenfeld, Craig McKenzie, and Michael Roy