In economics and business decision-making, a sunk cost (also known as retrospective cost) is a cost that has already been incurred and cannot be recovered. Sunk costs are contrasted with , which are future costs that may be avoided if action is taken. In other words, a sunk cost is a sum paid in the past that is no longer relevant to decisions about the future. Even though economists argue that sunk costs are no longer relevant to future rational decision-making, people in everyday life often take previous expenditures in situations, such as repairing a car or house, into their future decisions regarding those properties.
The bygones principle is grounded in the branch of normative decision theory known as rational choice theory, particularly in expected utility hypothesis. Expected utility theory relies on a property known as cancellation, which says that it is rational in decision-making to disregard (cancel) any state of the world that yields the same outcome regardless of one's choice. Past decisions—including sunk costs—meet that criterion.
The bygones principle can also be formalised as the notion of "separability". Separability requires agents to take decisions by comparing the available options in eventualities that can still occur, uninfluenced by how the current situation was reached or by eventualities that are precluded by that history. In the language of decision trees, it requires the agent's choice at a particular choice node to be independent of unreachable parts of the tree. This formulation makes clear how central the principle is to standard economic theory by, for example, founding the folding-back algorithm for individual sequential decisions and game-theoretical concepts such as sub-game perfection.
Until a decision-maker irreversibly commits resources, the prospective cost is an relevant cost and is properly included in any decision-making process. For instance, if someone is considering pre-ordering movie tickets, but has not actually purchased them yet, the cost remains avoidable.
Both retrospective and prospective costs could be either (continuous for as long as the business is operating and unaffected by output volume) or (dependent on volume). However, many economists consider it a mistake to classify sunk costs as "fixed" or "variable". For example, if a firm sinks $400 million on an enterprise software installation, that cost is "sunk" because it was a one-time expense and cannot be recovered once spent. A "fixed" cost would be monthly payments made as part of a service contract or licensing deal with the company that set up the software. The upfront irretrievable payment for the installation should not be deemed a "fixed" cost, with its cost spread out over time. Sunk costs should be kept separate. The "variable costs" for this project might include data centre power usage, for example.
There are cases in which taking sunk costs into account in decision-making, violating the bygones principle, is rational. For example, for a manager who wishes to be perceived as persevering in the face of adversity, or to avoid blame for earlier mistakes, it may be rational to persist with a project for personal reasons even if it is not the benefit of their company. Or, if they hold private information about the undesirability of abandoning a project, it is fully rational to persist with a project that outsiders think displays the fallacy of sunk cost.
Rego, Arantes, and Magalhães point out that the sunk cost effect exists in committed relationships. They devised two experiments, one of which showed that people in a relationship which they had invested money and effort in were more likely to keep that relationship going than end it; and in the second experiment, while people are in a relationship which they had invested enough time in, they tended to devote more time to the relationship. It also means people fall into the sunk cost fallacy. Although people should ignore sunk costs and make rational decisions when planning for the future, time, money, and effort often make people continue to maintain this relationship, which is equivalent to continuing to invest in failed projects.
According to evidence reported by De Bondt and Makhija (1988), managers of many utility companies in the United States have been overly reluctant to terminate economically unviable nuclear plant projects. In the 1960s, the nuclear power industry promised "energy too cheap to meter". Nuclear power lost public support in the 1970s and 1980s, when public service commissions around the nation ordered prudency reviews. From these reviews, De Bondt and Makhija find evidence that the commissions denied many utility companies even partial recovery of nuclear construction costs on the grounds that they had been mismanaging the nuclear construction projects in ways consistent with throwing good money after bad.
There is also evidence of government representatives failing to ignore sunk costs. The term "Concorde fallacy" derives from the fact that the British and French governments continued to fund the joint development of the costly Concorde supersonic airplane even after it became apparent that there was no longer an economic case for the aircraft. The British government privately regarded the project as a commercial disaster that should never have been started. Political and legal issues made it impossible for either government to pull out.
The idea of sunk costs is often employed when analyzing business decisions. A common example of a sunk cost for a business is the promotion of a brand name. This type of marketing incurs costs that cannot normally be recovered. It is not typically possible to later "demote" one's brand names in exchange for cash. A second example is research and development (R&D) costs. Once spent, such costs are sunk and should have no effect on future pricing decisions. A pharmaceutical company's attempt to justify high prices because of the need to recoup R&D expenses would be fallacious. The company would charge a high price whether R&D cost one dollar or one million. R&D costs and the ability to recoup those costs are a factor in deciding whether to spend the money on R&D in the first place.
Dijkstra and Hong proposed that part of a person's behavior is influenced by a person's current emotions. Their experiments showed that emotional responses benefit from the sunk cost fallacy. Negative influences lead to the sunk cost fallacy. For example, anxious people face the stress brought about by the sunk cost fallacy. When stressed, they are more motivated to invest in failed projects rather than take additional approaches. Their report shows that the sunk cost fallacy will have a greater impact on people under high load conditions and people's psychological state and external environment will be the key influencing factors.
The sunk cost effect may cause cost overrun. In business, an example of sunk costs may be an investment into a factory or research that now has a lower value or none. For example, $20 million has been spent on building a power plant; the value now is zero because it is incomplete (and no sale or recovery is feasible). The plant can be completed for an additional $10 million or abandoned and a different but equally valuable facility built for $5 million. Abandonment and construction of the alternative facility is the more rational decision, even though it represents a total loss of the original expenditure—the original sum invested is a sunk cost. If decision-makers are irrational or have the "wrong" (different) incentives, the completion of the project may be chosen. For example, politicians or managers may have more incentive to avoid the appearance of a total loss. In practice, there is considerable ambiguity and uncertainty in such cases, and decisions may in retrospect appear irrational that were, at the time, reasonable to the economic actors involved and in the context of their incentives. A decision-maker might make rational decisions according to their incentives, outside of efficiency or profitability. This is considered to be an incentive problem and is distinct from a sunk cost problem. Some research has also noted circumstances where the sunk cost effect is reversed; that is, where individuals appear irrationally eager to write off earlier investments in order to take up a new endeavor.Heath, Chip. "Escalation and de-escalation of commitment in response to sunk costs: The role of budgeting in mental accounting." Organizational Behavior and Human Decision Processes 62 (1995): 38-38.
This is a hazard for Sea captain or who may stick to a planned course even when it is leading to fatal disaster and they should abort instead. A famous example is the Torrey Canyon oil spill in which a tanker ran aground when its captain persisted with a risky course rather than accepting a delay. It has been a factor in numerous air crashes and an analysis of 279 approach and landing accidents (ALAs) found that it was the fourth most common cause, occurring in 11% of cases. Another analysis of 76 accidents found that it was a contributory factor in 42% of cases.
There are also two predominant factors that characterise the bias. The first is an overly optimism estimate of probability of success, possibly to reduce cognitive dissonance having made a decision. The second is that of personal responsibility: when you are personally accountable, it is difficult for you to admit that you were wrong.
Projects often suffer and delays due to the planning fallacy and related factors including excessive optimism, an unwillingness to admit failure, groupthink and Loss aversion of sunk costs.
Taken together, these results suggest that the sunk cost effect may reflect non-standard measures of utility, which is ultimately subjective and unique to the individual.
Take two mathematical functions:
While these functions are framed differently, regardless of the input "x", the outcome is analytically equivalent. Therefore, if a rational decision maker were to choose between these two functions, the likelihood of each function being chosen should be the same. However, a framing effect places unequal biases towards preferences that are otherwise equal.
The most common type of framing effect was theorised in Kahneman & Tversky, 1979 in the form of valence framing effects. This form of framing signifies types of framing. The first type can be considered positive where the "sure thing" option highlights the positivity whereas if it is negative, the "sure thing" option highlights the negativity, while both being analytically identical. For example, saving 200 people from a sinking ship of 600 is equivalent to letting 400 people drown. The former framing type is positive and the latter is negative.
Ellingsen, Johannesson, Möllerström and Munkammar have categorised framing effects in a social and economic orientation into three broad classes of theories. Firstly, the framing of options presented can affect internalised social norms or social preferences - this is called variable sociality hypothesis. Secondly, the social image hypothesis suggests that the frame in which the options are presented will affect the way the decision maker is viewed and will in turn affect their behaviour. Lastly, the frame may affect the expectations that people have about each other's behaviour and will in turn affect their own behaviour.
This has opened up more questions as to what might the evolutionary drivers be behind why the brain is capable of processing information in this way, what utility, if any, sensitivity to sunk costs may confer, and how might distinct circuits in the brain give rise to this sort of valuation depending on the framing of the question, circumstances of the environment, or state of the individual. Ongoing work is characterizing how neurons encode sensitivity to sunk costs, how sunk costs appear only after certain types of choices, and how sunk costs could contribute to mood burden.
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