A worst-case scenario is a concept in risk management wherein the planner, in planning for potential disasters, considers the most severe possible outcome that can reasonably be projected to occur in a given situation. Conceiving of worst-case scenarios is a common form of strategic planning, specifically scenario planning, to prepare for and minimize contingencies that could result in accidents, quality problems, or other issues.
Development and use
The worst-case scenario is "[o]ne of the most commonly used alternative scenarios". A risk manager
may request "a conservative risk estimate representing a worst-case
scenario" in order to determine the latitude they may exercise in
planning steps to reduce risks.
Generally, a worst-case scenario "is settled upon by agreeing that a
given worst case is bad enough. However, it is important to recognize
that no worst-case scenario is truly without potential nasty surprises". In other words, ‘[a] “worst-case scenario” is never the worst case’, both because situations may arise that no planner could reasonably foresee,
and because a given worst-case scenario is likely to consider only
contingencies expected to arise in connection with a particular
disaster. The worst-case scenario devised by a seismologist might be a
particularly bad earthquake, and the worst-case scenario devised by a
meteorologist might be a particularly bad hurricane, but it is unlikely
that either of them will devise a scenario where a particularly bad
storm occurs at the same time as a particularly bad earthquake.
The definition of a worst-case scenario varies by the field to which it is being applied. For example, in environmental engineering",
"[a] worst-case scenario is defined as the release of the largest
quantity of a regulated substance from a single vessel or process line
failure that results in the greatest distance to an endpoint".
In this field, "[a]s in other fields, the worst-case scenario is a
useful device when low probability events may result in a catastrophe
that must be avoided even at great cost, but in most health risk
assessments, a worst-case scenario is essentially a type of bounding
estimate". In computer science, the best, worst, and average case
of a given algorithm express what the resource usage is at least, at
most and on average, respectively. For many individuals, a worst case
scenario is one that would result in their own death.
Criticisms
A number of criticisms have been leveled against the use of worst-case scenarios.
In some cases, a conceivable worst-case scenario within a field may be
so far beyond the capacity of participants to deal with that it is not
worth the effort to develop or explore such a scenario; where this is
possible, it is "important to evaluate whether the development of a
worst-case scenario is reasonable and desirable".
Entities that rely on such scenarios in planning may be led to plan too
conservatively to take advantage of the usual absence of such
scenarios, and may waste resources preparing for highly unlikely
contingencies.
At the extreme, it has been argued that the use of worst-case scenarios
in disaster preparedness and training causes people to become
conditioned to set aside ethical concerns and to over-react to lesser
disasters.
