View source for Unintended consequences

{{Short description|Unforeseen outcomes of an action}}
{{About|the sociological concept|the novel|Unintended Consequences (novel)}}
{{redirect|Law of unintended consequences| the Wikipedia policy about law of unintended consequences|Wikipedia:Conflict of interest#Law of unintended consequences}}
{{Use mdy dates|date=September 2022}} 
[[Image:Rabbit-erosion.jpg|thumb|A [[gully erosion]] in Australia caused by rabbits, an unintended consequence of [[rabbits in Australia|their introduction as game animals]]]]
In the [[social sciences]], '''unintended consequences''' (sometimes '''unanticipated consequences''' or '''unforeseen consequences''', more colloquially called '''knock-on effects''') are outcomes of a purposeful action that are not intended or foreseen. The term was popularized in the 20th century by American [[sociologist]] [[Robert K. Merton]].<ref name="nytimes.com">[https://www.nytimes.com/2003/02/24/nyregion/robert-k-merton-versatile-sociologist-and-father-of-the-focus-group-dies-at-92.html Robert K. Merton, Versatile Sociologist and Father of the Focus Group, Dies at 92], Michael T. Kaufman, ''[[The New York Times]]''</ref>

Unintended consequences can be grouped into three types:
* ''Unexpected benefit'':  A positive unexpected benefit (also referred to as [[luck]], [[serendipity]], or a [[wikt:windfall|windfall]]).
* ''Unexpected drawback'':  An unexpected detriment occurring in addition to the desired effect of the policy (e.g., while [[irrigation]] schemes provide people with water for agriculture, they can increase [[waterborne diseases]] that have devastating health effects, such as [[schistosomiasis]]).
* ''Perverse result'': A perverse effect contrary to what was originally intended (when an intended solution makes a problem worse).

==History==
{{original research section|date=September 2024}}
===John Locke===
The idea of ''unintended consequences'' dates back at least to [[John Locke]] who discussed the unintended consequences of [[interest rate]] [[regulation]] in his letter to Sir John Somers, Member of Parliament.<ref>John Locke, [http://oll.libertyfund.org/titles/763#lf0128-04_head_002''The Works of John Locke in Nine Volumes''], (London: Rivington, 1824 12th ed.). Vol. 4.</ref>

===Adam Smith===
The idea was also discussed by [[Adam Smith]], the [[Scottish Enlightenment]], and [[consequentialism]] (judging by results).<ref>{{cite web|last=Smith|first=Adam|title=The Theory of Moral Sentiments|page=93|url=http://metalibri.wikidot.com/title:theory-of-moral-sentiments:smith-a}}</ref>

The [[Invisible hand|invisible hand theorem]] is an example of the unintended consequences of agents acting in their self-interest. As [[Andrew Stewart Skinner|Andrew S. Skinner]] puts it:<blockquote>"The individual undertaker ([[Entrepreneurship|entrepreneur]]), seeking the most efficient allocation of resources, contributes to overall [[economic efficiency]]; the merchant's reaction to price signals helps to ensure that the allocation of resources accurately reflects the structure of consumer preferences; and the drive to better our condition contributes to [[economic growth]]."<ref>{{Cite book |last=Stewart Skinner |first=Andrew |title=Handbook of the history of economic thought: insights on the founders of modern economics |date=2012 |publisher=Springer |editor=Jürgen G. Backhaus |isbn=978-1-4419-8336-7 |location=New York |page=171 |oclc=761868679}}</ref></blockquote>

===Marx and Engels===
Influenced by 19th century [[positivism]]<ref>{{harvnb|Saint-Upéry|2015|p= 146}}: Por supuesto, la raíz de esta posible mutación dogmática se puede identificar en la concepción de la «ciencia» de Marx, mezcla de Wissenschaft especulativa hegeliana y evolucionismo positivista típico del siglo XIX. [Of course, the root of this possible dogmatic mutation can be identified on Marx's conception of "science", a mix of speculative hegelian Wissenschaft and positivist evolutionism typical of the 19 century.]</ref> and [[Charles Darwin]]'s [[Theory of Evolution|evolution]], for both Friedrich Engels and Karl Marx, the idea of uncertainty and chance in social dynamics (and thus unintended consequences beyond results of perfectly defined laws) was only apparent, (if not rejected) since social actions were directed and produced by deliberate human intention.<ref>{{harvnb|Saint-Upéry|2015|p= 147}}: Es bien conocida la admiración de Marx y Engels por el autor de El origen de las especies y su ambición más o menos explícita de hacer para la evolución social lo que el científico británico había hecho para la evolución natural. Sin embargo, la interpretación de la selección natural por Marx era parcialmente defectiva. Reprochaba a Darwin el rol excesivo otorgado al azar en su esquema de evolución y defendía a veces en modo más bien implícito una especie de lamarckismo sociológico en el que la supuesta función político-ideológica o económica crea inevitablemente el órgano social adecuado en cada etapa del desarrollo de la humanidad. [Marx and Engels admiration for the author of On the Origin of Species and their more or less explicit ambition to do for social evolution what the british scientist did for natural evolution is well known. However, Marx's interpretation of natural selection was partially defective. He reproached Darwin for the excessive role given to chance in his scheme of evolution and defended -sometimes in a more implicit manner- a kind of sociological Lamarckism in which the supposed political-ideological or economic function inevitably creates the adequate social organ on each stage of human [historical] development.]</ref><ref>{{harvnb|Engels|1946| }}: In the history of society, on the contrary, the actors are all endowed with consciousness, are men acting with deliberation or passion, working towards definite goals; nothing happens without a conscious purpose, without an intended aim.</ref>

While discerning between the forces that generate changes in nature and those that generate changes in history in his discussion of [[Ludwig Feuerbach]], [[Friedrich Engels]] touched on the idea of (apparent) unintended consequences:

:{{Blockquote|In nature [...] there are only blind, unconscious agencies acting upon one another, [...] In the history of society, on the contrary, the actors are all endowed with consciousness, are men acting with deliberation or passion, working towards definite goals; nothing happens without a conscious purpose, without an intended aim. [...] For here, also, on the whole, in spite of the consciously desired aims of all individuals, accident apparently reigns on the surface. That which is willed happens but rarely; in the majority of instances the numerous desired ends cross and conflict with one another, or these ends themselves are from the outset incapable of realization, or the means of attaining them are insufficient. Thus the conflicts of innumerable individual wills and individual actions in the domain of history produce a state of affairs entirely analogous to [...] the realm of unconscious nature. The ends of the actions are intended, but the results which actually follow from these actions are not intended; or when they do seem to correspond to the end intended, they ultimately have consequences quite other than those intended. Historical events thus appear on the whole to be likewise governed by chance. But where on the surface accident holds sway, there actually it is always governed by inner, hidden laws, and it is only a matter of discovering these laws.|[[Ludwig Feuerbach and the End of Classical German Philosophy]] (Ludwig Feuerbach und der Ausgang der klassischen deutschen Philosophie), 1886.<ref>{{harvnb|Engels|1946| }}:</ref>|col2=|col3=}}

For his part, for [[Karl Marx]] what can be understood as unintended consequences are actually consequences that should be expected but are obtained unconsciously. These consequences (that no one consciously sought) would be (in the same way as it is for Engels<ref>{{harvnb|Vernon|1979|p= 69}}: Engels traces the occurrence of "what no one has willed" exclusively to the fact of conflict among actors</ref><ref name="Vernon">{{harvnb|Vernon|1979|p= 63}}: But the unintended consequences arising from diversity of ends, as we have noted already, are sometimes seen as emphatically good; they may be seen (as in Hayek) in  the light of immanent spontaneous cooperation, no less than (as in  Engels) in the light of destructive contradictions.</ref>) product of conflicts that confront actions from countless individuals. The deviation between the original intended goal and the product derived from conflicts would be a marxist equivalent to «unintended consequences.»<ref>{{harvnb|Vernon|1979|p= 58}}: "History is made in such a way that the final result always arises from conflicts between many individual wills... Thus there are innumerable intersecting forces, an infinite series of parallelograms of forces, which give rise to one resultant-the historical event... For what each individual wills is obstructed by everyone else, and what emerges is something that no one willed. Thus past history proceeds in the manner of a natural process... "</ref>

This social conflicts would happen as a result of a competitive society, and also lead society to sabotage itself and prevent historical progress.<ref>{{harvnb|Vernon|1979|p= 58}}: [For Marx and Engels] Unintended consequences are a feature not of "history" in general but of "past history", an expression of the inherently self-defeating tendencies of a competitive and inegalitarian society.</ref> Thus, historical progress (in Marxist terms) should eliminate these conflicts and make unintended consequences predictable.<ref>{{harvnb|Vernon|1979|p= 58}}: If this is so, then we may imagine a future order in which the rational coordination of efforts brings about a course of events which will have been consciously intended.</ref>

===Austrian School===
Unintended consequences are a common topic of study and commentary for the [[Austrian school of economics]] given its emphasis on [[methodological individualism]]. This is to such an extent that unexpected consequences can be considered as a distinctive part of Austrian tenets.<ref>{{harvnb|O'Driscoll Jr.|2004|p= 272}}: As Caldwell observes, "Menger's Principle of Economics is the founding document of the Austrian School of Economics, [...]" In it, Menger developed what became "fundamental Austrian tenets: the connection between time and error; the causal-genetic or compositive methodological approach; and the notion of unintended consequences".</ref>

====Carl Menger====
In "[[Principles of Economics (Menger book)|Principles of Economics]]", Austrian school founder [[Carl Menger]] (1840 - 1921) noted that the relationships that occur in the economy are so intricate that a change in the condition of a single [[Goods|good]] can have ramifications beyond that good. Menger wrote:

:{{Blockquote|If it is established that the existence of human needs capable of satisfaction is a prerequisite of goods-character [...] This principle is valid whether the goods can be placed in ''direct causal'' connection with the satisfaction of human needs, or derive their goods-character from a more or less indirect causal connection with the satisfaction of human needs. [...]<br/>Thus [[quinine]] would cease to be a good if the [[Malaria|diseases it serves to cure]] should disappear, since the only need with the satisfaction of which it is causally connected would no longer exist. But the disappearance of the usefulness of quinine would have the further consequence that a large part of the corresponding goods of higher order would also be deprived of their goods-character. The inhabitants of quinine-producing countries, who currently earn their livings by cutting and peeling [[cinchona]] trees, would suddenly find that not only their stocks of cinchona bark, but also, in consequence, their cinchona trees, the tools and appliances applicable only to the production of quinine, and above all the specialized labor services, by means of which they previously earned their livings, would at once lose their goods-character, since all these things would, under the changed circumstances, no longer have any causal relationship with the satisfaction of human needs.|Principles of Economics (Grundsätze der Volkswirtschaftslehre), 1871.<ref>{{harvnb|Menger|2007|pp= 64–65}}:</ref>|col2=|col3=}}

====Friedrich Hayek and Catallactics====
Economist and philosopher [[Friedrich Hayek]] (1899 – 1992) is another key figure in the Austrian School of Economics who is notable for his comments on unintended consequences.<ref>{{harvnb|O'Driscoll Jr.|2004|p= 279}}: [Hayek's] enduring contributions to the study of the unintended consequences of human action are among his most famous achievements. By elaborating that concept, Hayek developed a theory of institutions that spans economics and politics. A full appreciation of Hayek's ideas on unintended consequences would require an essay in its.</ref>

In "[[The Use of Knowledge in Society]]" (1945) Hayek argues that a centrally [[planned economy]] cannot reach the level of efficiency of the [[free market]] economy because the necessary (and pertinent) information for decision-making is not concentrated but dispersed among a vast number of agents.<ref>{{harvnb|Hayek|1996|}}:The peculiar character of the problem of a rational economic order is determined precisely by the fact that the knowledge of the circumstances of which we must make use never exists in concentrated or integrated form but solely as the dispersed bits of incomplete and frequently contradictory knowledge which all the separate individuals possess. [...] It is rather a problem of how to secure the best use of resources known to any of the members of society, for ends whose relative importance only these individuals know. Or, to put it briefly, it is a problem of the utilization of knowledge which is not given to anyone in its totality.</ref> Then, for Hayek, the price system in the free market allows the members of a society to anonymously coordinate for the most efficient use of resources, for example, in a situation of scarcity of a raw material, the price increase would coordinate the actions of an uncountable amount of individuals "in the right direction".<ref>{{harvnb|Hayek|1996|}}: The marvel is that in a case like that of a scarcity of one raw material, without an order being issued, without more than perhaps a handful of people knowing the cause, tens of thousands of people whose identity could not be ascertained by months of investigation, are made to use the material or its products more sparingly; i.e., they move in the right direction.</ref>

The development of this system of interactions would allow the progress of society,<ref>{{harvnb|Hayek|1996|}}:The price system is just one of those formations which man has learned to use (though he is still very far from having learned to make the best use of it) after he had stumbled upon it without understanding it. Through it not only a division of labor but also a coordinated utilization of resources based on an equally divided knowledge has become possible. [...] man has been able to develop that division of labor on which our civilization is based because he happened to stumble upon a method which made it possible.</ref> and individuals would carry it out without knowing all its implications, given the dispersion (or lack of concentration) of information.<ref>{{harvnb|Hayek|1996|}}:As Alfred Whitehead has said in another connection, "It is a profoundly erroneous truism, [...] that we should cultivate the habit of thinking what we are doing. The precise opposite is the case. Civilization advances by extending the number of important operations which we can perform without thinking about them." This is of profound significance in the social field. We make constant use of formulas, symbols, and rules whose meaning we do not understand and through the use of which we avail ourselves of the assistance of knowledge which individually we do not possess. We have developed these practices and institutions by building upon habits and institutions which have proved successful in their own sphere and which have in turn become the foundation of the civilization we have built up.</ref>

The implication of this is that the social order (which derives from social progress, which in turn derives from the economy),<ref>{{harvnb|Vernon|1979|p= 64}}: It turns out to be more difficult than may appear at first sight to define what it is that Hayek regards as the "order". Very frequently he refers to it as something "brought about" by multiple exchanges; it is something that "the market system leads to".</ref> would be result of a spontaneous cooperation and also an unintended consequence,<ref name=Vernon/> being born from a process of which no individual or group had all the information available or could know all possible outcomes.

In the Austrian school, this process of social adjustment that generates a social order in an unintendedly way is known as [[catallactics]].<ref>{{harvnb|Vernon|1979|pp= 63–64}}: No word seems quite right as a label for this category of unintended consequences [...] "Catallaxy" is the term which Hayek offers in place of "economy": the latter word, he argues, applies more properly to an organisation such as a business enterprise, and in applying it to the order which such enterprises compose we may be led to see it as a kind of large organisation, which it is not. It is an order spontaneously brought about by multiple transactions or exchanges (katallatein: "to exchange") among organisations. It is not a willed or designed or contrived thing, like an organisational hierarchy, but the unintended outcome of many independent decision.</ref>

For Hayek and the Austrian School, the number of individuals involved in the process of creating a social order defines the type of unintended consequence:<ref>{{harvnb|Vernon|1979|p= 64}}: whereas a spontaneous order rests upon decisions made locally by many actors whose aggregate knowledge is much greater than any single actor could have. Moreover, Hayek (unlike Popper) directs his objections not only against attempts to "organise" in a total or "utopian" way but also against more modest "interferences" with the order, which he alleges, always disrupt it. The role of legislation is only to provide a context of essentially general or abstract rules, rules not directed at particular ends nor imposed upon particular persons, which enable men to conduct their transactions in security. It follows necessarily that the general outcomes produced by the order are unintended. For it is no one's business to intend them</ref>

# If the process involves interactions and decision making of as many individuals (members of a society) as possible (thus gathering the greatest amount of knowledge dispersed among them), this process of "catallaxy" will lead to unexpected benefits (a social order and progress)
# On the other hand, attempts by individuals or limited groups (who lack all the necessary information) to achieve a new or better order, will end in unexpected drawbacks.

===Robert K. Merton===
Sociologist [[Robert K. Merton]] popularised this concept in the twentieth century.<ref name="nytimes.com"/><ref>{{cite web|title=Renowned Columbia Sociologist and National Medal of Science Winner Robert K. Merton Dies at 92 |url=http://www.columbia.edu/cu/news/03/02/robertKMerton.html|publisher=Columbia News}}</ref><ref>[http://www.asanet.org/footnotes/mar03/indextwo.html Robert K. Merton Remembered] Footnotes, American Sociological Association</ref><ref name="Merton"/>

In "The Unanticipated Consequences of Purposive Social Action" (1936), Merton tried to apply a systematic analysis to the problem of unintended consequences of deliberate acts intended to cause [[social change]]. He emphasized that his term ''purposive action'', "[was exclusively] concerned with 'conduct' as distinct from 'behavior.' That is, with action that involves motives and consequently a choice between various alternatives".<ref name="Merton">{{cite journal|last=Merton|first=Robert K.|title=The Unanticipated Consequences of Purposive Social Action|journal=[[American Sociological Review]]|volume=1|issue=6|pages=894–904|url=http://www.d.umn.edu/cla/faculty/jhamlin/4111/2111-home/CD/TheoryClass/Readings/MertonSocialAction.pdf |archive-url=https://web.archive.org/web/20130429205921/http://www.d.umn.edu/cla/faculty/jhamlin/4111/2111-home/CD/TheoryClass/Readings/MertonSocialAction.pdf |archive-date=2013-04-29 |url-status=live|access-date=2008-05-30|doi=10.2307/2084615|jstor=2084615|year=1936}}</ref> Merton's usage included deviations from what [[Max Weber]] defined as rational social action: instrumentally rational and value rational.<ref>{{cite book|last=Weber|first=Max|title=Economy and Society |url=https://archive.org/details/economysociety00webe|url-access=registration|publisher=University of California Press|date=1978|pages=[https://archive.org/details/economysociety00webe/page/24 24–25]|isbn=978-0-520-02824-1}}</ref> Merton also stated that "no blanket statement categorically affirming or denying the practical feasibility of ''all'' social planning is warranted."<ref name="Merton"/>

===Everyday usage===
More recently, the ''law of unintended consequences'' has come to be used as an adage or idiomatic warning that an intervention in a [[complex system]] tends to create unanticipated and often undesirable outcomes.<ref name="Norton ">{{cite encyclopedia |last=Norton |first=Rob |editor=David R. Henderson |editor-link=David R. Henderson |encyclopedia=[[Concise Encyclopedia of Economics]] |title=Unintended Consequences |url=http://www.econlib.org/library/Enc/UnintendedConsequences.html  |year=2008 |edition= 2nd |publisher=[[Library of Economics and Liberty]] |location=Indianapolis |isbn=978-0-86597-665-8 |oclc=237794267}}</ref><ref>{{cite journal|url=http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/mislj71&div=24&id=&page= |title= The Law of Unintended Consequences in Asbestos Litigation: How Efforts to Streamline the Litigation Have Fueled More Claims|journal=Mississippi Law Journal |volume=71 |page=531 |publisher=HeinOnline |access-date=2010-05-07|last1=Schwartz |first1=Victor E. |last2=Tedesco |first2=Rochelle M. }}</ref><ref>{{cite journal|url=http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/flsulr28&div=36&id=&page= |title=28 Florida State University Law Review 2000–2001 Mandatory Minimum Sentences: Exemplifying the Law of Unintended Consequences Comment |journal=Florida State University Law Review |volume=28 |page=935 |publisher=Heinonline.org |date=1993-06-18 |access-date=2012-11-21|last1=Mascharka |first1=Christopher }}</ref><ref>{{cite journal|url=http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/antil65&div=47&id=&page= |title= The Effect of Twenty Years of Hart-Scott-Rodino on Merger Practice: A Case Study in the Law of Unintended Consequences Applied to Antitrust Legislation|journal=Antitrust Law Journal |volume=65 |page=865 |publisher=HeinOnline |access-date=2010-05-07|last1=Sims |first1=Joe |last2=Herman |first2=Deborah P. }}</ref>

Akin to [[Murphy's law]], it is commonly used as a wry or humorous warning against the [[hubris]]tic belief that humans can fully control the world around them, not to presuppose a belief in predestination or a lack or a disbelief in that of free will.

==Causes==
Possible causes of unintended consequences include the world's inherent [[complexity]] (parts of a system responding to changes in the environment), [[perverse incentive]]s, human [[stupidity]], [[self-deception]], failure to account for human nature, or other [[cognitive bias|cognitive]] or [[emotional bias|emotional]] biases. As a sub-component of complexity (in the scientific sense), the chaotic nature of the universe—and especially its quality of having small, apparently insignificant changes with far-reaching effects (e.g., the [[butterfly effect]])—applies.

In 1936, [[Robert K. Merton]] listed five possible causes of unanticipated consequences:<ref>{{cite book|author=Merton, Robert K|title=On Social Structure and Science|series=Heritage of Sociology Series |publisher=[[The University of Chicago Press]]|year=1996|url=http://press.uchicago.edu/ucp/books/book/chicago/O/bo3626245.html|access-date=2018-05-16}}</ref>

* Ignorance, making it  impossible to anticipate everything, thereby leading to incomplete analysis.
* Errors in analysis of the problem or following habits that worked in the past but may not apply to the current situation.
* Immediate interests overriding long-term interests.
* Basic values which may require or prohibit certain actions even if the long-term result might be unfavourable (these long-term consequences may eventually cause changes in basic values).
* [[Self-defeating prophecy]], or, the fear of some consequence which drives people to find solutions before the problem occurs, thus the non-occurrence of the problem is not anticipated.

In addition to Merton's causes, psychologist [[Stuart Vyse]] has noted that [[groupthink]], described by [[Irving Janis]], has been blamed for some decisions that result in unintended consequences.<ref>{{cite journal |last1=Vyse |first1=Stuart|author-link=Stuart Vyse |title=Can Anything Save Us from Unintended Consequences? |journal=[[Skeptical Inquirer]] |date=2017 |volume=41 |issue=4 |pages=20–23 |url=https://www.csicop.org/specialarticles/show/can_anything_save_us_from_unintended_consequences |archive-url=https://web.archive.org/web/20180919223200/https://www.csicop.org/specialarticles/show/can_anything_save_us_from_unintended_consequences |archive-date=2018-09-19 |access-date=19 September 2018}}</ref>

==Types==
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===Unexpected benefits===
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The creation of "[[no-man's land]]s" during the [[Cold War]], in places such as the border between Eastern and Western Europe, and the [[Korean Demilitarized Zone]], has led to large natural habitats.<ref>{{cite news |url=https://www.independent.co.uk/environment/nature/from-iron-curtain-to-green-belt-how-new-life-came-to-the-death-strip-1686294.html |title=From Iron Curtain to Green Belt: How new life came to the death strip |publisher=Independent.co.uk |date=2009-05-17 |access-date=2010-05-07 |location=London}}</ref><ref>{{cite news |author=Kate Connolly |url=https://www.theguardian.com/travel/2009/jul/04/germany-green-line-iron-curtain |title=From Iron Curtain to Green Belt |newspaper=Guardian |date=2009-07-04 |access-date=2010-05-07 |location=London}}</ref><ref>{{cite web |url=http://europeangreenbelt.org/001.route_ce.html |title=European Green Belt |publisher=European Green Belt |access-date=2010-05-07 |archive-url=https://web.archive.org/web/20100129132357/http://europeangreenbelt.org/001.route_ce.html |archive-date=2010-01-29 }}</ref>

[[File:Oriskany July 2008 -57.jpg|thumb|Sea life on the wreck of the sunken [[USS Oriskany (CV-34)|USS ''Oriskany'']]]]
The sinking of ships in shallow waters during wartime has created many [[artificial reef|artificial coral reefs]], which can be scientifically valuable and have become an attraction for recreational divers. This led to the [[deliberate sinking]] of retired ships for the purpose of replacing coral reefs lost to [[global warming]] and other factors.<ref>{{cite web |url=http://www.dnr.maryland.gov/dnrnews/pressrelease2008/020708a.html |title=Maryland Artificial Reef Initiative Celebrates 1 Year Anniversary |publisher=Dnr.maryland.gov |date=2008-02-07 |access-date=2010-05-07}}</ref><ref>{{cite web |url=https://www.nbcnews.com/id/wbna18853363 |title=Sinking ships will boost tourism, group says&nbsp;– News&nbsp;– NBC News |work=NBC News |date=2007-05-25 |access-date=2010-05-07}}</ref><ref>{{cite web |url=http://www.thenational.ae/apps/pbcs.dll/article?AID=/20090921/NATIONAL/709209873/1042/FOREIGN |archive-url=https://web.archive.org/web/20150509132717/http://www.thenational.ae/apps/pbcs.dll/article?AID=%2F20090921%2FNATIONAL%2F709209873%2F1042%2FFOREIGN |archive-date=2015-05-09 |title=Life after death on the ocean floor&nbsp;– The National Newspaper |publisher=Thenational.ae |date=2009-09-21 |access-date=2010-05-07 }}</ref><ref>{{cite web |url=http://cbs4.com/local/vandenberg.fish.key.2.1250653.html |title=Sea Life Flourishing On Vandenberg Wreck Off Keys |publisher=cbs4.com |date=2009-10-15 |access-date=2010-05-07 |archive-url=https://web.archive.org/web/20091227174325/http://cbs4.com/local/vandenberg.fish.key.2.1250653.html |archive-date=2009-12-27 }}</ref><ref>{{cite web |url=http://www.cdnn.info/news/industry/i061227.html |title=CDNN: Diver Wants to Sink Old Navy Ships off California Coast |publisher=Cdnn.info |date=2006-12-27 |access-date=2010-05-07}}</ref>

In [[medicine]], most [[Medication|drugs]] have unintended consequences ('[[side effect]]s') associated with their use. However, some are beneficial. For instance, [[aspirin]], a [[pain reliever]], is also an [[anticoagulant]] that can help prevent [[myocardial infarction|heart attacks]] and reduce the severity and damage from [[thrombotic stroke]]s.<ref name=BBC15Feb2001>{{cite news |url=https://news.bbc.co.uk/2/hi/health/1168850.stm |title=BBC 15 February 2001, ''Aspirin heart warning'' |work=BBC News |date=2001-02-15 |access-date=2010-05-07}}</ref> Beneficial side effects have also lead to [[off-label use]] {{Ndash}}prescription or use of a drug for an unlicensed purpose. Famously, the drug [[Viagra]] was developed to lower blood pressure, with its use for treating [[erectile dysfunction]] being discovered as a side effect in clinical trials.

In [[Papal conclave|papal conclave]] journalism, Cardinal [[Fridolin Ambongo Besungu]] of [[Kinshasa]] in the [[Democratic Republic of Congo]], the elected leader of all the bishops of Africa (including Madagascar), by early 2024 had come to be regarded as [[papabile]] for his adroit handling of the issue of blessing [[same sex unions]], to which he is staunchly opposed.<ref>{{Cite web|url=https://cruxnow.com/news-analysis/2024/01/on-the-cobra-effect-and-congos-ambongo-as-an-emerging-papal-candidate|title=On the 'Cobra Effect' and Congo's Ambongo as an emerging papal candidate|date=January 31, 2024|website=Crux}}</ref>

===Unexpected drawbacks===
The implementation of a profanity filter by [[AOL]] in 1996 had the unintended consequence of blocking residents of [[Scunthorpe]], [[North Lincolnshire]], England, from creating accounts because of a [[false positive]].<ref name="risks digest">{{cite journal |url=http://catless.ncl.ac.uk/Risks/18.07.html#subj3 |title=AOL censors British town's name! |journal=The Risks Digest |publisher=ACM Committee on Computers and Public Policy |date=25 April 1996 |author=Clive Feather |volume=18 |issue=7 |editor=Peter G. Neumann}}</ref> The accidental [[censorship]] of innocent language, known as the [[Scunthorpe problem]], has been repeated and widely documented.<ref>{{cite web |url=http://blog.siliconglen.com/2010/03/bbc-fail-my-correct-name-is-not.html |title=BBC fail – my correct name is not permitted |first1=Craig |last1=Cockburn |publisher=blog.siliconglen.com |date=9 March 2010 |access-date=24 February 2011 |archive-date=July 16, 2011 |archive-url=https://web.archive.org/web/20110716071000/http://blog.siliconglen.com/2010/03/bbc-fail-my-correct-name-is-not.html |url-status=dead }}</ref><ref name="butt">{{cite news |url=https://www.telegraph.co.uk/news/newstopics/howaboutthat/2667634/The-Clbuttic-Mistake-When-obscenity-filters-go-wrong.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/news/newstopics/howaboutthat/2667634/The-Clbuttic-Mistake-When-obscenity-filters-go-wrong.html |archive-date=2022-01-12 |url-access=subscription |url-status=live |title=The Clbuttic Mistake: When obscenity filters go wrong |last=Moore |first=Matthew |date=2 September 2008 |work=The Daily Telegraph |access-date=4 April 2010 |location=London}}{{cbignore}}</ref><ref>{{cite news |url=http://www.switched.com/2008/08/01/town-censors-its-name/ |title=F-Word Town's Name Gets Censored By Internet Filter |access-date=27 July 2011}}</ref>

In 1990, the Australian state of [[Victoria (Australia)|Victoria]] made [[bicycle helmet|safety helmets]] mandatory for all bicycle riders. While there was a reduction in the number of head injuries, there was also an unintended reduction in the number of juvenile cyclists—fewer cyclists obviously leads to fewer injuries, [[Ceteris paribus|all else being equal]]. The risk of death and serious injury per cyclist seems to have increased, possibly because of [[risk compensation]].<ref>{{Cite web|url=https://www.cyclehelmets.org/1241.html|title=Head Injuries and Helmet Laws in Australia and New Zealand|website=www.cyclehelmets.org}}</ref> Research by Vulcan et al. found that the reduction in juvenile cyclists was because the youths considered wearing a bicycle helmet unfashionable.<ref>{{cite journal |last1=Cameron |first1=Maxwell H. |last2=Vulcan |first2=A. Peter |last3=Finch |first3=Caroline F. |last4=Newstead |first4=Stuart V. |date=June 1994 |title=Mandatory bicycle helmet use following a decade of helmet promotion in Victoria, Australia—an evaluation |journal=Accident Analysis and Prevention |volume=26 |issue=3 |pages=325–37 |doi=10.1016/0001-4575(94)90006-X |pmid=8011045}}</ref> A health-benefit model developed at [[Macquarie University]] in Sydney suggests that, while helmet use reduces "the risk of head or brain injury by approximately two-thirds or more", the decrease in exercise caused by reduced cycling as a result of helmet laws is counterproductive in terms of net health.<ref>
[http://docplayer.net/storage/64/52001739/1538888219/17X_qhDVpvxBJrWz1V_yZA/52001739.pdf de Jong. Piet (2012), "Evaluating the Health Benefit of Mandatory Bicycle Helmet Laws", ''Risk Analysis'', Vol.32, No.5, p.782-790.]</ref>

[[Prohibition in the United States|Prohibition in the 1920s United States]], 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. Similarly, the [[war on drugs]], intended to suppress the [[illegal drug trade]], instead increased the power and profitability of drug cartels who became the primary source of the products.<ref>Juan Forero, "Colombia's Coca Survives U.S. plan to uproot it", The New York Times, August 19, 2006</ref><ref>Don Podesta and Douglas Farah, "Drug Policy in Andes Called Failure," ''[[Washington Post]]'', March 27, 1993</ref><ref name="streatfeild">{{cite web |author=Dominic Streatfeild |title=Source Material for ''Cocaine: An Unauthorized Biography'': Interview between Milton Friedman and Dominic Streatfeild |date=June 2000 |url=http://www.dominicstreatfeild.com/2010/11/08/interview-with-milton-friedman/ |publisher=Dominicstratfeild |access-date=2012-11-21 |archive-url=https://web.archive.org/web/20121113201345/http://www.dominicstreatfeild.com/2010/11/08/interview-with-milton-friedman/ |archive-date=2012-11-13 }}</ref><ref>{{cite web |title=An open letter |url=http://www.prohibitioncosts.org/endorsers.html |publisher=Prohibition Costs |access-date=2008-02-20 |archive-url=https://web.archive.org/web/20060110171453/http://www.prohibitioncosts.org/endorsers.html |archive-date=2006-01-10 }}</ref>

In [[CIA]] [[jargon]], "[[Blowback (intelligence)|blowback]]" describes the unintended, undesirable consequences of covert operations, such as the funding of the [[Afghan Mujahideen]] and the destabilization of Afghanistan contributing to the rise of the [[Taliban]] and [[Al-Qaeda]].<ref name=BinLiner>{{cite web |url=http://www.msnbc.com/news/190144.asp |title=Bin Laden comes home to roost |website=[[MSNBC]] |access-date=2009-12-30 |archive-url=https://web.archive.org/web/19981202035147/http://www.msnbc.com/news/190144.asp |archive-date=December 2, 1998 }}</ref><ref>{{cite web |url=https://www.theatlantic.com/issues/96may/blowback.htm |title=Blowback – 96.05 |publisher=Theatlantic.com |access-date=2012-11-21|date=May 1996 }}</ref><ref>{{cite news |author=Peter Beaumont |url=http://www.observer.co.uk/international/story/0,6903,787999,00.html |title=Why 'blowback' is the hidden danger of war &#124; World news |publisher=The Observer |access-date=2012-11-21 |newspaper=The Guardian |date=2002-09-08 |archive-date=July 18, 2008 |archive-url=https://web.archive.org/web/20080718104724/http://www.observer.co.uk/international/story/0,6903,787999,00.html |url-status=dead }}</ref>

The introduction of [[Introduced species|exotic]] animals and plants for food, for decorative purposes, or to control unwanted species often leads to more harm than good done by the introduced species.
* The introduction of [[rabbits in Australia]] and [[New Zealand]] for food was followed by an explosive growth in the rabbit population; rabbits have become a major [[feral]] [[Pest (animal)|pest]] in these countries.<ref>{{cite web |url=http://agspsrv34.agric.wa.gov.au/programs/app/barrier/history.htm |archive-url=https://web.archive.org/web/20050722133944/http://agspsrv34.agric.wa.gov.au/programs/app/barrier/history.htm |archive-date=2005-07-22 |title=The State Barrier Fence of Western Australia |publisher=The State Barrier Fence Project |access-date=2009-10-09 }}</ref><ref>{{cite web |url=http://christchurchcitylibraries.com/Kids/NZBirdsAnimals/Rabbits/ |title=Rabbits: Introduction into New Zealand |publisher=Christchurch City Libraries |access-date=2009-10-09}}</ref>
* [[Cane toad]]s, introduced into Australia to control canefield pests, were unsuccessful and have become a major pest in their own right.
* [[Kudzu]], introduced to the US as an ornamental plant in 1876<ref name="Kudzu: Love It or Run">[[Smithsonian Magazine]] [https://archive.today/20130202145614/http://www.smithsonianmag.com/science-nature/kudzu-abstract.html Kudzu: Love It or Run]</ref> and later used to prevent erosion in earthworks, has become a major problem in the Southeastern United States. Kudzu has displaced native plants and has effectively taken over significant portions of land.<ref name="Illinois">{{cite web |url=http://www.news.uiuc.edu/NEWS/05/1020kudzu.html |title=Fast-growing kudzu making inroads in Illinois, authorities warn |access-date=April 28, 2008 |publisher=News Bureau, University of Illinois at Urbana-Champaign |year=2005 |author=Molly McElroy |archive-url=https://web.archive.org/web/20080706015032/http://www.news.uiuc.edu/news/05/1020kudzu.html |archive-date=July 6, 2008 |df=mdy-all }}</ref><ref name="blaustein">{{cite web |url=https://www.srs.fs.usda.gov/pubs/ja/ja_blaustein001.pdf |archive-url=https://web.archive.org/web/20061006031255/http://www.srs.fs.usda.gov/pubs/ja/ja_blaustein001.pdf |archive-date=2006-10-06 |url-status=live |title=Kudzu's invasion into Southern United States life and culture |access-date=August 20, 2007 |publisher=United States Department of Agriculture |year=2001 |author=Richard J. Blaustein }}</ref>

The protection of the steel industry in the United States reduced production of steel in the United States, increased costs to users, and increased unemployment in associated industries.<ref>{{cite journal |url=http://www.gpo.gov/fdsys/pkg/CHRG-107hhrg81372/html/CHRG-107hhrg81372.htm |title=The Unintended Consequences of Increased Steel Tariffs on American Manufacturers |journal=Committee on Small Business, House of Representatives, 107th United States Congress |location=Washington, DC |date=July 23, 2002 |number=Serial No. 107–66 |publisher=[[U.S. Government Printing Office]] |access-date=October 26, 2014}}</ref><ref>{{cite web |url=http://citac.info/study/citac_2002jobstudy_020703.pdf |archive-url=https://web.archive.org/web/20030403044706/http://www.citac.info/study/citac_2002jobstudy_020703.pdf |archive-date=2003-04-03 |url-status=live |publisher=CITAC Foundation/Trade Partnership Worldwide, LLC |title=The Unintended Consequences of U.S. Steel Import Tariffs: A Quantification of the Impact During 2002 |first1=Dr. Joseph |last1=Francois |first2=Laura M. |last2=Baughman |date=February 4, 2003 |location=Washington DC |access-date=October 26, 2014}}</ref>

===Perverse results===
{{See also|Perverse incentive|Perverse subsidies}}
<!--Do NOT add examples, see talk! There are already too many examples. Discuss in talk first before adding an example. Otherwise it will be removed. -->[[File:Streisand Estate.jpg|thumb|The infamous photo of the Streisand Estate]]
In 2003, [[Barbra Streisand]] unsuccessfully sued Kenneth Adelman and Pictopia.com for posting a photograph of her home online.<ref>{{cite news |url=https://www.bbc.co.uk/news/magazine-28562156 |title=The perils of the Streisand effect |newspaper=BBC News |access-date=9 September 2015|date=2014-07-31 |last1=Parkinson |first1=Justin }}</ref> Before the lawsuit had been filed, only 6 people had downloaded the file, two of them Streisand's attorneys.<ref>Tentative ruling, page 6, stating, "Image 3850 was download six times, twice to the Internet address of counsel for plaintiff". In addition, two prints of the picture were ordered — one by Streisand's counsel and one by Streisand's neighbor. http://www.californiacoastline.org/streisand/slapp-ruling-tentative.pdf</ref> The lawsuit drew attention to the image, resulting in 420,000 people visiting the site.<ref name=rogers>{{cite web |url=http://www.californiacoastline.org/news/sjmerc5.html |title=Photo of Streisand home becomes an Internet hit |access-date=2007-06-15 |last=Rogers |first=Paul |date=2003-06-24 |work=[[San Jose Mercury News]]|via= californiacoastline.org}}</ref> The [[Streisand Effect]] was named after this incident, describing when an attempt to censor or remove a certain piece of information instead draws attention to the material being suppressed, resulting in the material instead becoming widely known, reported on, and distributed.<ref name=London>{{cite web |last=Canton |first=David |url=http://www.lfpress.ca/cgi-bin/publish.cgi?p=111404&x=articles&s=shopping |title=Today's Business Law: Attempt to suppress can backfire |archive-url=https://archive.today/20070927014240/http://www.lfpress.ca/cgi-bin/publish.cgi?p=111404&x=articles&s=shopping |archive-date=2007-09-27 |work=[[London Free Press]] |date=November 5, 2005 |access-date=July 21, 2007 |quote=The "Streisand effect" is what happens when someone tries to suppress something and the opposite occurs. The act of suppressing it raises the profile, making it much more well known than it ever would have been}}</ref>

Passenger-side [[airbag]]s in motorcars were intended as a safety feature, but led to an increase in child fatalities in the mid-1990s because small children were being hit by airbags that deployed automatically during collisions. The supposed solution to this problem, moving the child seat to the back of the vehicle, led to an increase in the number of children forgotten in unattended vehicles, some of whom died under extreme temperature conditions.<ref>{{cite magazine |url=https://time.com/hot-car-death/ |magazine=Time |first1=Justin |last1=Worland/Ridgefield |title=Who's To Blame For Hot Car Deaths? |date=2014-09-02}}</ref>

Risk compensation, or the [[Risk compensation|Peltzman effect]], occurs after implementation of safety measures intended to reduce injury or death (e.g. bike helmets, seatbelts, etc.). People may feel safer than they really are and take additional risks which they would not have taken without the safety measures in place. This may result in no change, or even an increase, in morbidity or mortality, rather than a decrease as intended.

According to an [[anecdote]], the British government, concerned about the number of venomous cobra snakes in [[Delhi]], offered a bounty for every dead cobra. This was a successful strategy as large numbers of snakes were killed for the reward. Eventually, enterprising people began breeding cobras for the income. When the government became aware of this, they scrapped the reward program, causing the cobra breeders to set the now-worthless snakes free. As a result, the wild cobra population further increased. The apparent solution for the problem made the situation even worse, becoming known as the [[Cobra effect]].

[[Theobald Mathew (temperance reformer)|Theobald Mathew]]'s temperance campaign in 19th-century [[Ireland]] resulted in thousands of people vowing never to drink [[Alcoholic drink|alcohol]] again. This led to the consumption of [[diethyl ether]], a much more dangerous intoxicant—owing to its high flammability—by those seeking to become intoxicated without breaking the letter of their pledge.{{Dubious|date=June 2023}}<ref>{{cite web |url=http://www.worldwidewords.org/weirdwords/ww-eth1.htm |title=Etheromaniac |publisher=World Wide Words |date=2006-09-09 |access-date=2012-11-21}}</ref><ref>{{Cite news|url=https://unintendedconsequenc.es/substitutions-temperance-movement-ether/|title=Substitutions - The Temperance Movement and Ether - Unintended Consequences|date=2018-09-16|work=Unintended Consequences|access-date=2018-09-16|language=en-US}}</ref>

It was thought that adding south-facing [[Conservatory (greenhouse)|conservatories]] to British houses would reduce energy consumption by providing extra insulation and warmth from the sun. However, people tended to use the conservatories as living areas, installing heating and ultimately increasing overall energy consumption.<ref>"Our innate ability to think of new ways to use energy" Professor [[Tadj Oreszczyn]]. Summer 2009 edition of 'palette', UCL's journal of sustainable cities.</ref>

A reward for [[ghost net|lost nets]] found along the Normandy coast was offered by the French government between 1980 and 1981. This resulted in people vandalizing nets to collect the reward.<ref>Andres, Von Brandt (1984) ''Fish catching methods of the world'' {{ISBN|978-0-685-63409-7}}.</ref>

Beginning in the 1940s and continuing into the 1960s, the Canadian federal government gave Quebec $2.75 per day per psychiatric patient for their cost of care, but only $1.25 a day per orphan. The perverse result is that the orphan children were diagnosed as mentally ill so Quebec could receive the larger amount of money. This psychiatric misdiagnosis affected up to 20,000 people, and the children are known as the [[Duplessis Orphans]] in reference to the Premier of Quebec who oversaw the scheme, [[Maurice Duplessis]].<ref>{{cite web |url=https://www.cbc.ca/news/canada/quebec-ombudsman-says-duplessis-orphans-right-1.173120 |title=CBC |work=google.com |access-date=2 November 2023}}</ref><ref>{{cite web |url=https://news.google.com/newspapers?id=1WNWAAAAIBAJ&pg=6929%2C5814760 |title=The Spokesman-Review |work=google.com |access-date=9 September 2015}}</ref><ref>{{cite web |url=https://news.google.com/newspapers?id=DeceAAAAIBAJ&pg=6753%2C1774080 |title=Sarasota Herald-Tribune |work=google.com |access-date=9 September 2015}}</ref><ref>{{cite web |url=https://news.google.com/newspapers?id=lT9TAAAAIBAJ&pg=6732%2C2759782 |title=The Prescott Courier |work=google.com |access-date=9 September 2015}}</ref>

There have been attempts to curb the consumption of sugary beverages by imposing a tax on them. However, a study found that the reduced consumption was only temporary.<!-- Then how long?  --> Also, there was an increase in the consumption of beer among households.<ref name="Wansink">{{Cite SSRN |last1=Wansink|first1=Brian|last2=Hanks|first2=Andrew S.|last3=Just|first3=David R.|date=2012-05-26|title=From Coke to Coors: A Field Study of a Fat Tax and Its Unintended Consequences|ssrn=2079840}}</ref>

The [[New Jersey Childproof Handgun Law]], which was intended to protect children from accidental discharge of firearms by forcing all future firearms sold in [[New Jersey]] to contain [[smart gun|"smart" safety features]], has delayed, if not stopped entirely, the introduction of such firearms to New Jersey markets. The wording of the law caused significant public backlash,<ref>{{cite news| url=http://www.inc.com/joseph-steinberg/smartguns-what-you-need-to-know.html |work=Inc. | title=Smartguns: What You Need to Know | date=January 11, 2016 | access-date=January 11, 2016 |author=Joseph Steinberg }}</ref> fuelled by [[National Rifle Association|gun rights lobbyists]],<ref>{{cite web | url=http://www.highbrowmagazine.com/4363-why-nra-opposes-smart-guns | title=Why the NRA Opposes Smart Guns | date=15 October 2014 | access-date=26 December 2015 | author=Trumbly, Katie}}</ref><ref>{{cite web | url=https://www.theverge.com/2014/5/5/5683504/gun-control-the-nra-wants-to-take-smart-guns-away | title=Gun control: the NRA wants to take America's smart guns away | website=[[The Verge]] | date=5 May 2014 | access-date=26 December 2015 | author=Jeffries, Adrianne}}</ref> and several shop owners offering such guns received death threats and stopped stocking them.<ref>{{cite news|url=https://www.washingtonpost.com/local/california-smart-gun-store-prompts-furious-backlash/2014/03/06/43432058-a544-11e3-a5fa-55f0c77bf39c_story.html|title=Calif. store backs away from smart guns after outcry from 2nd Amendment activists|first=Michael S.|last=Rosenwald| date =6 March 2014 |newspaper=The Washington Post}}</ref><ref name=wp-marylandsmart>{{cite news |first=Michael S. |last=Rosenwald |title=Maryland dealer, under pressure from gun-rights activists, drops plan to sell smart gun |url=https://www.washingtonpost.com/local/maryland-dealer-will-defy-gun-rights-advocates-by-selling-nations-first-smart-gun/2014/05/01/564efa48-d14d-11e3-937f-d3026234b51c_story.html |newspaper=The Washington Post |date=1 May 2014 |access-date=8 May 2014}}</ref> In 2014, 12 years after the law was passed, it was suggested the law be repealed if gun rights lobbyists agree not to resist the introduction of "smart" firearms.<ref>{{Cite web| last = Montopoli| first = Brian| title = N.J. Democrat: We will reverse smart gun law if NRA plays ball| work = MSNBC| access-date = 2014-05-22| date = 2014-05-02| url = http://www.msnbc.com/all/democrat-we-will-reverse-smart-gun-law}}</ref>

[[Prohibition of drugs|Drug prohibition]] can lead [[Illegal drug trade|drug traffickers]] to [[Preference (economics)|prefer]] stronger, more dangerous substances, that can be more easily smuggled and distributed than other, less concentrated substances.<ref>{{Cite news| issn = 0261-3077| last = Kassam| first = Ashifa| title = 'Dose as small as a grain of sand can kill you': alarm after Canada carfentanil bust| work = The Guardian| access-date = 2017-11-12| date = 2017-11-12| url = https://www.theguardian.com/world/2017/nov/12/carfentanil-bust-canada-fentanyl-opioid-crisis-dangers}}</ref>

Televised drug prevention advertisements may lead to increased drug use.<ref>{{Cite journal |last1=Hornik |first1=Robert |last2=Jacobsohn |first2=Lela |last3=Orwin |first3=Robert |last4=Piesse |first4=Andrea |last5=Kalton |first5=Graham |date=December 2008 |title=Effects of the National Youth Anti-Drug Media Campaign on Youths |journal=American Journal of Public Health |volume=98 |issue=12 |pages=2229–2236 |doi=10.2105/AJPH.2007.125849 |issn=0090-0036 |pmc=2636541 |pmid=18923126}}</ref>

Increasing usage of [[search engine]]s, also including recent [[Image retrieval|image search]] features, has contributed in the ease of which media is consumed. Some [[Abnormal psychology|abnormalities]] in usage may have shifted preferences for pornographic film actors, as the producers began using [[search engine optimization|common search queries or tags]] to label the actors in new roles.<ref>{{Cite web| last = Kline| first = Matthew| title = How SEO has changed the porn industry| work = Mashable| date = 11 August 2017| access-date = 2017-08-12| url = http://mashable.com/2017/08/11/seo-of-porn/}}</ref>

The passage of the [[Stop Enabling Sex Traffickers Act]] has led to a reported increase in risky behaviors by sex workers as a result of quashing their ability to seek and screen clients online, forcing them back onto the streets or into the [[dark web]]. The ads posted were previously an avenue for advocates to reach out to those wanting to escape the trade.<ref>{{Cite magazine | url=https://www.rollingstone.com/culture/features/sesta-fosta-forces-sex-trafficking-victims-streets-dark-web-w520720 |title = New Law Forces Sex-Trafficking Victims to Streets, Dark Web|magazine = [[Rolling Stone]]|date = 2018-05-25}}</ref>

The use of [[precision guided munition]]s meant to reduce the rate of [[collateral damage|civilian casualties]] encouraged armies to narrow their safety margins, and increase the use of deadly force in densely populated areas. This in turn increased the danger to uninvolved civilians, who in the past would have been out of the line of fire because of armies' aversion of using higher-risk weaponry in densely populated areas.<ref name="Levi 2019">{{Cite news |last=לוי |first=יגיל |date=2019-12-25 |script-title=he:במערב חשבו שחימוש מדויק יצמצם פגיעה באזרחים. זה לא קרה |language=he |newspaper=Haaretz |url=https://www.haaretz.co.il/magazine/the-edge/.premium-MAGAZINE-1.8316333 |access-date=2021-05-25}}</ref> The perceived ability to operate precision weaponry from afar (where in the past heavy munitions or troop deployment would have been needed) also led to the expansion of the list of potential targets.<ref name="Levi 2019" /> As put by [[Michael Walzer]]: "Drones not only make it possible for us to get at our enemies, they may also lead us to broaden the list of enemies, to include presumptively hostile individuals and militant organizations simply because we can get at them—even if they aren't actually involved in attacks against us."<ref>{{Cite journal |last=Walzer |first=Michael |date=2016-09-01 |title=Just & Unjust Targeted Killing & Drone Warfare |journal=Daedalus |volume=145 |issue=4 |pages=12–24 |doi=10.1162/DAED_a_00408 |s2cid=57563272 |issn=0011-5266|doi-access=free }}</ref> This idea is also echoed by [[Grégoire Chamayou]]: "In a situation of moral hazard, military action is very likely to be deemed 'necessary' simply because it is possible, and possible at a lower cost."<ref>{{Cite book |last=Chamayou |first=Grégoire |title=Drone theory |publisher=Penguin |year=2015 |isbn=978-0-241-97034-8 |location=London |oclc=903527249}}</ref>{{page needed|date=November 2023}}

After ''[[Dobbs v. Jackson Women's Health Organization]]'' (2022) overturned ''[[Roe v. Wade]]'' (1973), the number of abortions in the United States increased and the number of births fell, due to the [[Freedom of movement under United States law|right to travel]] between states.<ref>{{Cite web|url=https://www.nytimes.com/2024/10/22/upshot/abortions-rising-state-bans.html|title=Abortions Have Increased, Even for Women in States With Rigid Bans, Study Says|date=October 22, 2024|website=The New York Times|first1=Claire Cain|last1=Miller|first2=Margot|last2=Sanger-Katz|first3=Josh|last3=Katz|access-date=December 2, 2024}}</ref><ref>{{Cite book|title=After Dobbs: How the Supreme Court Ended Roe but Not Abortion|date=2025|first1=David S.|last1=Cohen|first2=Carole|last2=Joffe|publisher=Beacon Press |isbn=978-0807017661 |quote=When the Supreme Court overturned ''Roe v. Wade'' in June 2022, many feared it meant the end of abortion access in the United States. Yet the courageous work of people on the ground has allowed abortion to survive post-Dobbs in ways that no one predicted. ... Taking place across three intervals throughout 2022—pre-Dobbs in early 2022, right after Dobbs, and then six months later—these interviews showcase how nimble thinking on the part of providers, growth and new delivery models of abortion pills, and the never-ending work of those who help with abortion travel and funding have ensured most people who want them are still getting abortions, even without Roe.}}</ref><ref>{{Cite web|url=https://www.cdc.gov/nchs/products/databriefs/db507.htm|title=Births in the United States, 2023|date=August 2024|access-date=March 14, 2025|website=Centers for Disease Control}}</ref>

===Other===
According to [[Lynn Townsend White|Lynn White]], the invention of the horse [[stirrup]] enabled new patterns of warfare that eventually led to the development of [[feudalism]] (see [[Stirrup Thesis]]).<ref>{{Cite book |title=Medieval technology and social change |author=Lynn White Jr. |date=1962 |publisher=Clarendon Press |isbn=978-0-19-500266-9 |location=Oxford |oclc=390344 |url-access=registration |url=https://archive.org/details/medievaltechnolo00whit }}</ref>

==Perverse consequences of environmental intervention==
Almost all [[environmental problem]]s, from chemical [[pollution]] to [[global warming]], are the unexpected consequences of the application of modern technologies. [[Traffic congestion]], deaths and injuries from car accidents, [[air pollution]], and global warming are unintended consequences of the invention and large scale adoption of the [[automobile]]. [[Hospital infection]]s are the unexpected<!-- There are no more "unexpected". They are to be expected at all times.  --> side-effect of [[antibiotic resistance]], and even human [[population growth]] leading to [[environmental degradation]] is the side effect of various technological (i.e., [[Agricultural revolution (disambiguation)|agricultural]] and [[industrial revolution|industrial]]) revolutions.<ref>{{cite book |author1=Huesemann, Michael H. |title=Technofix: Why Technology Won't Save Us or the Environment |author2=Joyce A. Huesemann |publisher=New Society Publishers |year=2011 |isbn=978-0-86571-704-6 |location=Gabriola Island, British Columbia, Canada |page=464 |chapter=Chapter 1, "The Inherent Unavoidability and Unpredictability of Unintended Consequences", and Chapter 2, "Some Unintended Consequences of Modern Technology" |chapter-url=http://www.newtechnologyandsociety.org}}</ref>

Because of the complexity of [[ecosystems]], deliberate changes to an ecosystem or other environmental interventions will often have (usually negative) unintended consequences. Sometimes, these effects cause permanent [[irreversible change]]s. Examples include:
[[File:Everybody Comes to Beat Sparrows.jpg|thumb|Chinese poster encouraging children to attack sparrows|alt=Chinese poster promoting the Four Pests campaign; a boy with a red neckerchief aims a slingshot at an off-frame overhead target, and a girl next to him looks at the target as well. There is a village in the background. There is a Chinese slogan "大家都来打麻雀" in red letters at the footer.]]
* During the [[Four Pests campaign]], Maoist China ordered the killing of sparrows, as well as rats, flies, and mosquitoes. The campaign was successful in reducing the sparrow population; however, in their absence, locust populations previously kept in check by sparrow predation grew out of control and came to infest crops. Rice yields were substantially decreased; the campaign was one of the causes of the [[Great Chinese Famine]].<ref>{{cite book|first=Frank|last= Dikotter|title=Mao's Great Famine|location=New York|publisher=Walker & Co.|year=2010|page=188}}</ref><ref>{{cite web |last1=Carl |first1=Seaver |title=How Killing Sparrows Led to Great Famines in China |url=https://www.historydefined.net/how-killing-sparrows-led-to-one-of-the-greatest-famines-in-history/ |website=History Defined |date=April 26, 2022 |access-date=9 December 2022}}</ref><ref>{{cite news |last1=Weston |first1=Pheobe |title=What happens when humans meddle with nature? |url=https://www.theguardian.com/environment/2022/nov/22/what-happens-when-humans-meddle-with-nature-aoe |work=The Guardian |date=November 22, 2022 |access-date=9 December 2022}}</ref> 
* During the [[Great Plague of London]] a killing of dogs and cats was ordered. If left untouched, they would have made a significant reduction in the rat population that carried the fleas which transmitted the disease.<ref>Moote, Lloyd and Dorothy: ''The Great Plague: the Story of London's most Deadly Year'', Baltimore, 2004. p. 115.</ref>
* The installation of [[smokestack]]s to decrease pollution in local areas, resulting in spread of pollution at a higher altitude, and [[acid rain]] on an international scale.<ref name="Likens, G. E. 1979">{{cite journal | last1 = Likens | first1 = G. E. | last2 = Wright | first2 = R. F. | last3 = Galloway | first3 = J. N. | last4 = Butler | first4 = T. J. | year = 1979 | title = Acid rain | journal = Sci. Am. | volume = 241 | issue = 4| pages = 43–51 | doi=10.1038/scientificamerican1079-43| bibcode = 1979SciAm.241d..43L }}</ref><ref>{{cite journal | last1 = Likens | first1 = G. E. | year = 1984 | title = Acid rain: the smokestack is the "smoking gun | journal = Garden | volume = 8 | issue = 4| pages = 12–18 }}</ref>
* After about 1900, public demand led the US government to fight [[forest fire]]s in the American West, and set aside land as national forests and parks to protect them from fires. This policy led to fewer fires, but also led to growth conditions such that, when fires did occur, they were much larger and more damaging. Modern research suggests that this policy was misguided, and that a certain level of wildfires is a natural and important part of [[forest ecology]].<ref name="How The Smokey Bear Effect Led To Raging Wildfires">{{cite web|last=Joyce|first=Christopher|title=How The Smokey Bear Effect Led To Raging Wildfires|url=https://www.npr.org/2012/08/23/159373691/how-the-smokey-bear-effect-led-to-raging-wildfires|work=npr.org|access-date=27 August 2012}}</ref>
*Side effects of [[climate engineering]] to [[climate change mitigation|counter global warming]] could involve even further warming as a consequence of reflectivity-reducing [[afforestation]] or [[crop yield]] reductions and [[rebound effect]]s after [[solar dimming]] measures with even more accelerated warming.<ref name="Vidal 2014">{{cite web | last=Vidal | first=John | title=Geoengineering side effects could be potentially disastrous, research shows | website=The Guardian | date=2014-02-25 | url=http://www.theguardian.com/environment/2014/feb/25/geoengineering-side-effects-potentially-disastrous-scientists | access-date=2019-09-23}}</ref><ref name="Yang Dobbie Ramirez-Villegas Feng pp. 11,786–11,795">{{cite journal | last1=Yang | first1=Huiyi | last2=Dobbie | first2=Steven | last3=Ramirez-Villegas | first3=Julian | last4=Feng | first4=Kuishuang | last5=Challinor | first5=Andrew J. | last6=Chen | first6=Bing | last7=Gao | first7=Yao | last8=Lee | first8=Lindsay | last9=Yin | first9=Yan | last10=Sun | first10=Laixiang | last11=Watson | first11=James | last12=Koehler | first12=Ann-Kristin | last13=Fan | first13=Tingting | last14=Ghosh | first14=Sat | title=Potential negative consequences of geoengineering on crop production: A study of Indian groundnut | journal=Geophysical Research Letters | publisher=American Geophysical Union (AGU) | volume=43 | issue=22 | date=2016-11-19 | issn=0094-8276 | doi=10.1002/2016gl071209 | pages=11,786–11,795| pmid=28190903 | pmc=5267972 | bibcode=2016GeoRL..4311786Y | doi-access=free }}</ref>

==See also==
{{Columns-list|
* {{annotated link|Boomerang effect (psychology)}}
* {{annotated link|Collateral damage}}
* {{annotated link|Domino effect}}
* {{annotated link|Dutch disease}}
* {{annotated link|Heterogony of ends}}
* {{annotated link|Ethics in mathematics}}
* {{annotated link|Externality}}
* {{annotated link|Instrumental and value-rational action}}
* {{annotated link|Knightian uncertainty}}
* {{annotated link|Map–territory relation}}
* {{annotated link|Moral hazard}}
* {{annotated link|Parable of the broken window}}
* {{annotated link|Rebound effect}}
* {{annotated link|Rebound effect (conservation)}}
* {{annotated link|Parkinson's law}}
* {{annotated link|Streisand effect}}
* {{annotated link|System accident}}
* {{annotated link|Systemantics}}
* {{annotated link|Technology assessment}}
* {{annotated link|The Rhetoric of Reaction}} (appearing as the "perversity thesis")
* {{annotated link|Tragedy of the commons}}
* {{annotated link|Virtuous circle and vicious circle}}
}}

==References==
{{Reflist}}

==Bibliography==
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* {{cite web |last1=Hayek |first1=Friedrich |author-link1=Friedrich Hayek |date=1 May 1996 |orig-date=1945 |title=The Use of Knowledge in Society |url=https://fee.org/articles/the-use-of-knowledge-in-society/ |language=en |website=[[Foundation for Economic Education]] |access-date=14 May 2023}}
* {{cite journal |last1=Vernon |first1=Richard |date=February 1979 |title=Unintended Consequences |journal=[[Political Theory (journal) |Political Theory]] |language=en |publisher=[[SAGE Publishing]] |location=[[Newbury Park, California]] |volume=7 |issue=1 |pages=57–73 |doi=10.1177/009059177900700104 |jstor=190824}}
* {{cite book |last1=Engels |first1=Friedrich |author-link1=Friedrich Engels |publisher=Progress Publishers |year=1946 |orig-date=1886 |chapter=Part 4: Marx |title=Ludwig Feuerbach and the End of Classical German Philosophy |url=https://www.marxists.org/archive/marx/works/1886/ludwig-feuerbach/index.htm |language=en |via=[[Marxists Internet Archive]] |isbn=978-1-4102-2345-6 |oclc=45655872 |access-date=16 May 2023}}
* {{cite journal |last=Saint-Upéry |first=Marc |author-link=:fr:Marc Saint-Upéry |date=March–April 2015 |editor1-last=Cucchi |editor1-first=Silvina |editor2-last=Grieco |editor2-first=Florencia |title=Tres derroteros del marxismo: pseudociencia, historia, ontología |trans-title=Three paths of Marxism: pseudoscience, history, ontology |url=https://library.fes.de/pdf-files/nuso/ |format=PDF |journal=Nueva Sociedad |language=es |location=Buenos Aires |issue=256 |pages=145–163 |issn=0251-3552 |access-date=19 May 2023}}
* [https://www.jstor.org/stable/2084615 The Unanticipated Consequences of Purposive Social Action] by Robert K. Merton, ''[[American Sociological Review]]'', Vol 1 Issue 6, Dec 1936, pp.&nbsp;894–904
* [https://www.econlib.org/library/Enc/UnintendedConsequences.html Unintended Consequences] entry in ''[[Concise Encyclopedia of Economics]]''
* [https://www.academia.edu/838612/Unintended_Consequences_of_Green_Technologies Unintended Consequences of Green Technologies]
* Mica Adriana, Peisert Arkadiusz, Winczorek Jan (eds), (2011), ''Sociology and the Unintended. Robert Merton Revisited'', [[Peter Lang (publisher)|Peter Lang]], Frankfurt am Main.
* Huesemann, Michael H., and Joyce A. Huesemann (2011). [http://www.newtechnologyandsociety.org ''Technofix: Why Technology Won't Save Us or the Environment''], Chapter 1, "The Inherent Unavoidability and Unpredictability of Unintended Consequences", Chapter 2, "Some Unintended Consequences of Modern Technology", and Chapter 4, "In Search of Solutions I: [[Radar detector|Counter-Technologies]] and Social Fixes", [[New Society Publishers]], Gabriola Island, British Columbia, Canada, {{ISBN|0-86571-704-4}}, 464 pp.
* Edward Tenner, ''[[Why Things Bite Back|Why Things Bite Back: Technology and the Revenge of Unintended Consequences]],'' [[Vintage 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]], October 5–7, 1992''.
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* [http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=12794 "Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use"]

==External links==
* [https://unintendedconsequenc.es/blog/ Unintended Consequences blog]

{{unintended consequences}}
{{Chaos theory}}
{{Authority control}}

[[Category:Adages]]
[[Category:Complex systems theory]]
[[Category:Concepts in ethics]]
[[Category:Consequentialism]]
[[Category:Futures studies]]
[[Category:Intention]]
[[Category:Principles]]
[[Category:Risk management]]
[[Category:Social sciences terminology]]
[[Category:Robert K. Merton]]