Unintended consequences

An erosion gully in Australia caused by rabbits. The release of rabbits in Australia for hunting purposes has had serious unintended ecological consequences.

In the social sciences, unintended consequences (sometimes unanticipated consequences or unforeseen consequences) are outcomes that are not the ones intended by a purposeful action. The concept has long existed but was named and popularised in the 20th century by American sociologist Robert K. Merton.^[1]

Unintended consequences can be roughly grouped into three types:

A positive, unexpected benefit (usually referred to as luck, serendipity or a windfall).
A negative, 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).
A perverse effect contrary to what was originally intended (when an intended solution makes a problem worse), such as when a policy has a perverse incentive that causes actions opposite to what was intended.

History

The idea of unintended consequences dates back at least to Adam Smith, the Scottish Enlightenment, and consequentialism (judging by results).^[2] However, it was the sociologist Robert K. Merton who popularized this concept in the twentieth century.^[1]^[3]^[4]^[5]

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".^[5] Merton also stated that "no blanket statement categorically affirming or denying the practical feasibility of all social planning is warranted."^[6]

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.^[7]^[8]^[9]^[10] 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.

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, failure to account for human nature or other cognitive or 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.

Robert K. Merton listed five possible causes of unanticipated consequences:^[11]

Ignorance (It is impossible to anticipate everything, thereby leading to incomplete analysis)
Error (Incorrect analysis of the problem or following habits that worked in the past but may not apply to the current situation)
Immediate interest, which may override long-term interests
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)
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

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.^{[citation needed]} Likewise 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, have created large natural habitats.^[12]^[13]^[14]
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.^[15]^[16]^[17]^[18]^[19]
Controversial research by John J. Donohue and Steven Levitt suggests that legalized abortion in the United States (by reducing the numbers of unwanted children), can account for much of the drop in crime rates that occurred in the 1990s. Their paper, The Impact of Legalized Abortion on Crime, presents evidence that 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.^[20]
In medicine, most drugs have unintended consequences associated with their use ('side effects'). 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.^[21] The existence of beneficial side effects also leads to off-label use—prescription or use of a drug for an unlicensed purpose.

Unexpected drawbacks

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, all else being equal. Research by Vulcan et al. found that the reduction in juvenile cyclists was because the youths considered wearing a bicycle helmet unfashionable.^[22] 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 helmets laws is counterproductive in terms of net health.^[23]
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 organizations producing alcohol were well funded and hence also increased their other activities. The War on Drugs, intended to suppress the illegal drug trade, instead consolidates the profitability of drug cartels.^[24]^[25]^[26]^[27]

In CIA jargon, "blowback" describes the unintended, undesirable consequences of covert operations, for example: covert funding of the Afghan Mujahideen, which contributed to the rise of Al-Qaeda.^[28]
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.^[29]^[30]
- Cane toads, introduced into Australia to control canefield pests, were unsuccessful and have become a major pest in their own right.
- Kudzu, introduced as an ornamental plant 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.^[31]^[32]
- Africanized bee: In 1957, while searching for an increase in honey production, Warwick E. Kerr accidentally released Africanized bees in Brazil. The "especially defensive" Africanized bee species expanded into the north and south Americas.^{[citation needed]}

Perverse results

The term Streisand Effect is applied to the internet phenomenon that 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.^[33] The fact that a piece of information is being restricted assigns to it a previously nonexistent value in the eyes of the public.
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.^{[citation needed]} Legislators later stiffened penalties for leaving the scene of an accident.
Rent control in many major cities is intended to make housing more accessible for lower income tenants. However, most economists believe it can reduce the quantity and quality of housing.^[34] Landlords often circumvent the rent control by extracting bribes in the form of key money.
Theobald Mathew's temperance campaign in 19th-century Ireland (in which thousands of people vowed never to drink alcohol again) led to the consumption of diethyl ether, a much more dangerous intoxicant, by those unwilling to break their pledge.^[35]
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.^[36]

Public policy produces many unintended consequences, and one celebrated example in the UK National Health Service is the policy that patients arriving at accident and emergency centres must be treated within a define period after entry. During busy periods this has led to patients being made to wait outside in the ambulances in which they arrived, thus removing the ambulances from service.