Unintended consequences are outcomes that are not (or not limited to) what the actor intended in a particular situation. The unintended results may be foreseen or unforeseen, but they should be the logical or likely results of the action. For example, students of history often conjecture that if the Treaty of Versailles had not imposed such harsh conditions on Germany, World War II would not have occurred. From this perspective, one might consider the war an unintended consequence of the treaty.

One may class unintended consequences into roughly three types:

• a positive unexpected benefit, usually referred to as serendipity or a windfall
• a negative or perverse effect, that may be contrary to what was originally intended
• a potential source of problems, such as described by Murphy's law

Discussions of unintended consequences usually refer to the situation of perverse results. This situation often arises because a policy has a perverse incentive and causes actions contrary to what is desired.

The law of unintended consequences

The "law of unintended consequences" (also called the "law of unforeseen consequences") states that any purposeful action will produce some unintended consequences. A classic example is a bypass — a road built to relieve traffic congestion on a congested road — that attracts new development and with it more traffic, resulting in two congested streets instead of one.

This maxim is not a scientific law; it is more in line with Murphy's law as a warning against the hubristic belief that humans can fully control the world around them. Stated in other words, each cause has more than one effect, and these effects will invariably include at least one unforeseen side effect. The unintended side effect can potentially be more significant than any of the intended effects.

History

The idea of unintended consequences dates back at least to Adam Smith, the Scottish Enlightenment, and consequentialism (judging by results). However, it was the sociologist Robert K. Merton who popularized this concept in the twentieth century.

In his 1936 paper, "The Unanticipated Consequences of Purposive Social Action", Merton tried to apply a systematic analysis to the problem of "unanticipated consequences" of "purposive social action". He emphasized that his term "purposive action… [is exclusively] concerned with 'conduct' as distinct from 'behavior.' That is, with action that involves motives and consequently a choice between various alternatives".¹ Merton also stated that "no blanket statement categorically affirming or denying the practical feasibility of all social planning is warranted."²

Causes

Possible causes of unintended consequences include the world's inherent complexity (parts of a system responding to changes in the environment), perverse incentives, human stupidity, self-deception or other cognitive or emotional biases.

Robert K. Merton listed five possible causes of unanticipated consequences:³

1. Ignorance (It is impossible to anticipate everything, thereby leading to incomplete analysis)
2. Error (Incorrect analysis of the problem or following habits that worked in the past but may not apply to the current situation)
3. Immediate interest, which may override long-term interests
4. Basic values may require or prohibit certain actions even if the long-term result might be unfavorable (these long-term consequences may eventually cause changes in basic values)
5. Self-defeating prophecy (Fear of some consequence drives people to find solutions before the problem occurs, thus the non-occurrence of the problem is unanticipated)

Examples

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Unexpected benefits

• The medieval policy of setting up large hunting reserves for the nobility has preserved green space, often as parks, throughout England and other places in Europe. Likewise the creation of "no-man's lands" in places such as the Korean Demilitarized Zone have created unique natural habitats. The same has occurred with minefields in the Falkland Islands: since birds are too light to trigger the mines, the minefields have become de facto bird sanctuaries.

• The sinking of ships in shallow waters during wartime has created many artificial coral reefs: beautiful, scientifically valuable and an attraction for recreational divers.

• Research carried out by John J. Donohue and Steven Levitt suggests that legalized abortion in the United States can account for much of the drop in crime rates that occurred in the 1990s.⁴ States that legalized abortion before Roe v. Wade saw correspondingly earlier drops in crime; and states where abortion is common saw greater drops in crime than states where abortion is rare. Most convincingly, they found that "in high abortion states, only arrests of those born after abortion legalization fall relative to low abortion states."

• In medicine, most drugs have unintended consequences associated with their use, which are known as 'side effects'. Many are harmful and are more precisely called 'adverse effects'. However, some are beneficial—for instance, aspirin, a pain reliever, can also thin the blood and help to prevent heart attacks. The existence of beneficial side effects also leads to off label use — prescription or use of a drug for a non-intended purpose.

Perverse results

• The Streisand Effect occurs when an attempt to censor or remove a certain piece of information (such as a photograph, document, etc.) instead causes the information to become widely known and distributed. The fact that a piece of information is being restricted assigns to it a previously nonexistent value in the eyes of the public.

• The introduction of rabbits into Australia for sport led to an explosive growth in the rabbit population; rabbits have become a major feral pest in Australia. The same has occurred in New Zealand.

• Along the same lines, kudzu has become a major problem in the South Eastern United States since its introduction as a way of preventing erosion in earthworks. Kudzu has displaced native plants, and has effectively taken over in significant portions of land.

• The stiffening of penalties for driving while intoxicated in the United States in the 1980s led, at first, to an increase in hit and run accidents, most of which were believed to have been drunken drivers trying to escape the law. Legislators later stiffened penalties for leaving the scene of an accident.

• In 1990, the State of Victoria (Australia) made safety helmets mandatory for all bicycle riders. Together with a reduction in the absolute number of head injuries, there was also an unexpected reduction in the number of juvenile cyclists. Research by Vulcan et al. found that the reduction in juvenile cyclists was because the youths considered wearing a bicycle helmet unfashionable.⁵

• Prohibition in the 1920s U.S., originally enacted to suppress the alcohol trade, drove many small-time alcohol suppliers out of business and consolidated the hold of large-scale organized crime over the illegal alcohol industry. Since alcohol was still popular, criminal organisations producing alcohol were well funded and hence also increased their other activities. The War on Drugs, intended to suppress the illegal drug trade, has likewise consolidated the hold of organized drug cartels over the illegal drug industry.^{citation needed}

• In CIA jargon, "blowback" describes the unintended, undesirable consequences of covert operations. Examples include:
  • Operation Ajax, which contributed to the 1979 Iranian Revolution & the Iran hostage crisis
  • Covert funding of the Mujahideen, which led to the rise of the Taliban

• Rent control leads in the long run to housing shortages, and drops in housing availability and quality. It may even lead to the creation of slum areas where owners permit rental property to run down until it becomes uninhabitable.

• Father Mathew's temperance campaign in 19th-century Ireland – in which thousands of people vowed never to drink alcohol again – led to the consumption of ether, a much more dangerous intoxicant, by those unwilling to break their pledge.

• Government biofuel subsidies – especially of corn-based ethanol – may actually harm the environment and increase CO2 emissions, and raise the price and reduce the availability of food grains.⁶

Failure mode and effects analysis

Failure mode and effects analysis (FMEA) is a fault tree method (first developed for systems engineering) that examines potential failures in products or processes. It may be used to evaluate risk management priorities for mitigating known threat-vulnerabilities.

FMEA helps select remedial actions that reduce cumulative impacts of life-cycle consequences (risks) from a systems failure (fault).⁷

Purposeful gaming to achieve unintended consequences

Another more restrictive use of the term unintended consequence is when a mechanism that has been installed with the intention of producing one result is used to produce a different (and often conflicting) result. One games the system when one acts in such a way that gains advantages by exploiting rules which were intended for some other purpose. For example, computer viruses, worms, and other such plagues are unintended consequences of the way certain computer systems are designed. Spam is an unintended consequence of the way the email system works. The preceding computer examples illustrate this sense of unintended consequence in that spammers hijack a mechanism, e.g., email, intended for interpersonal communication, for advertising.

This sense of unintended consequence excludes, for example, the proliferation of rabbits in Australia as an unintended consequence of their introduction. The proliferation of rabbits was indeed an unexpected (and unintended) consequence of their introduction, but it did not result from the exploitation of a mechanism for some other purpose. The intent to "game the system" distinguishes this interpretation of unintended consequence from such a broader interpretation of unintended consequence as a result of simple historical contingency. See the Museum of Unintended Consequences for more examples.

See also

References

External links

Look up knock-on effect in
Wiktionary, the free dictionary.

• The Unanticipated Consequences of Purposive Social Action by Robert K. Merton, American Sociological Review, Vol 1 Issue 6, Dec 1936, pp.894-904
• Atlantic magazine article: "Blowback"
• Observer article: Why 'blowback' is the hidden danger of war
• MSNBC article on Bin Laden and blowback
• Unintended Consequences
• Museum of Unintended Consequences
• Edward Tenner, Why Things Bite Back: Technology and the Revenge of Unintended Consequences, Vantage Books, 1997.
• Tomislav V. Kovandzic, John Sloan III, and Lynne M. Vieraitis. Unintended Consequences of Politically Popular Sentencing Policy: The Homicide-Promoting Effects of 'Three Strikes' in U.S. Cities (1980-1999). Criminology & Public Policy, Vol 1, Issue 3, July 2002.
• Vulcan, A.P., Cameron, M.H. & Heiman, L., "Evaluation of mandatory bicycle helmet use in Victoria, Australia", 36th Annual Conference Proceedings, Association for the Advancement of Automotive Medicine, Oct 5-7, 1992.
• Vulcan, A.P., Cameron, M.H. & Watson, W.L., "Mandatory Bicycle Helmet Use: Experience in Victoria, Australia", World Journal of Surgery, Vol.16, No.3, (May/June 1992), pp.389-397.