Unintended consequences

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.[2]

The idea was also discussed by Adam Smith, the Scottish Enlightenment, and consequentialism (judging by results).[3]

Sociologist Robert K. Merton popularised this concept in the twentieth century.[1][4][5][6]

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".[6] Merton's usage included deviations from what Max Weber defined as rational social action: instrumentally rational and value rational.[7] Merton also stated that "no blanket statement categorically affirming or denying the practical feasibility of all social planning is warranted."[8]

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.[9][10][11][12]

Akin to Murphy's law, it is commonly used as a wry or humorous warning against the hubristic belief that humans can fully control the world around them.

The creation of "no-man's lands" 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.[15][16][17]

The sinking of ships in shallow waters during wartime has created many artificial coral reefs, which can be scientifically valuable and have become an attraction for recreational divers. Retired ships have been purposely sunk in recent years, in an effort to replace coral reefs lost to global warming and other factors.[18][19][20][21][22]

In medicine, most drugs have unintended consequences ('side effects') associated with their use. However, some are beneficial. For instance, aspirin, a pain reliever, is also an anticoagulant that can help prevent heart attacks and reduce the severity and damage from thrombotic strokes.[23] The existence of beneficial side effects also leads to off-label use—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.

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 due to a false positive.[24] The accidental censorship of innocent language, known as the Scunthorpe problem, has been repeated and widely documented.[25][26][27]

In 1990, the Australian state of Victoria made 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, assuming all else being equal. The risk of death and serious injury per cyclist seems to have increased, possibly due to risk compensation.[28] Research by Vulcan, et al. found that the reduction in juvenile cyclists was because the youths considered wearing a bicycle helmet unfashionable.[29] 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.[30]

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.[31][32][33][34]

In CIA jargon, "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.[35][36][37]

The introduction of 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 in these countries.[38][39]
• Cane toads, 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[40] 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.[41][42]

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.[43][44]

In 2003, Barbra Streisand unsuccessfully sued Kenneth Adelman and Pictopia.com for posting a photograph of her home online.[45] Before the lawsuit had been filed, only 6 people had downloaded the file, two of them Streisand's attorneys.[46] The lawsuit drew attention to the image, resulting in 420,000 people visiting the site.[47] 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.[48]

Passenger-side airbags 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.[49]

Risk compensation, or the 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's temperance campaign in 19th-century Ireland resulted in thousands of people vowing never to drink alcohol again. This led to the consumption of diethyl ether, a much more dangerous intoxicant — due to its high flammability — by those seeking to become intoxicated without breaking the letter of their pledge.[50][51]

It was thought that adding south-facing 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.[52]

A reward for 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.[53]

Beginning in the 1940s and continuing into the 1960s, the Canadian federal government gave the Catholic Church in Quebec $2.25 per day per psychiatric patient for their cost of care, but only $0.75 a day per orphan. The perverse result is that the orphan children were diagnosed as mentally ill so the church 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.[54][55][56]

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. Also, there was an increase in the consumption of beer among households.[57]

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" 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,[58] fuelled by gun rights lobbyists,[59][60] and several shop owners offering such guns received death threats and stopped stocking them[61][62] 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.[63]

Drug prohibition can lead drug traffickers to prefer stronger, more dangerous substances, that can be more easily smuggled and distributed than other, less concentrated substances.[64]

Televised drug prevention advertisements may lead to increased drug use.[65]

Increasing usage of search engines, also including recent image search features, has contributed in the ease of which media is consumed. Some abnormalities in usage may have shifted preferences for pornographic film actors, as the producers began using common search queries or tags to label the actors in new roles.[66]

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.[67]

According to Lynn White, the invention of the horse stirrup enabled new patterns of warfare that eventually led to the development of feudalism (see Great Stirrup Controversy).[68]