Forecasting completion times: what a plan alone cannot establish
In Basel, a date for an industrial transfer, a delivery or a scientific validation often commits several organisations. The management question is precise: on what basis should a deadline be accepted when the plan looks coherent but previous experience suggests delays?
What the literature establishes
Roger Buehler, Dale Griffin and Michael Ross (1994, Journal of Personality and Social Psychology) show that, in the tasks studied, people underestimate their completion times and favour future scenarios over past experience. In one of their studies, explicitly connecting the forecast to previous experience eliminates this bias. The finding therefore concerns how an estimate is constructed, not just how much information is available.
The mechanism: looking at the project from the outside
Daniel Kahneman and Dan Lovallo (1993, Management Science) offer a theoretical analysis distinguishing the inside view, focused on a project's particular features, from the outside view, based on comparable situations. A detailed scenario can make success understandable without establishing its probability or timing. Historical comparison requires consideration of difficulties that the plan may not describe.
The premature conclusion
One might conclude that every deadline simply needs a buffer. These papers justify neither a universal multiplier nor the automatic replacement of technical judgement with a historical average. The point is to compare the two perspectives and justify discrepancies, particularly when a change in process or regulatory framework reduces comparability. (our executive and employee training programmes)
What the evidence cannot guarantee
The tasks examined in the experimental study do not reproduce the interdependencies of a pharmaceutical programme or international R&D. The theoretical paper does not, by itself, validate this approach in life sciences or Rhine logistics. In practice, a historical record restricted to completed projects, or using inconsistent definitions of start and finish, can distort the reference.
A practical check in Bâle
As part of SHR's decision-making programme, an exercise applicable in Basel is to select a category of recurring milestones in pharma, life sciences, Rhine logistics or international R&D. For each new milestone, record before committing the team's estimated duration, the durations of comparable cases using identical start and finish definitions, and the final estimate after comparison, retaining the original estimate. At completion, compare the median absolute error of the initial and final estimates, in days, for the same milestones, and report those still open separately. This measure makes it possible to check whether the comparison actually improves local forecasts, without attributing every change to the method in advance. To go further: explore the Decision-making training in Basel, or browse our executive and employee training programmes in Switzerland.
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