Learn more about Unintended consequence
Unintended consequences are situations where an action results in an outcome that is not (or not only) what is intended. The unintended results may be foreseen or unforeseen, but they should be the logical or likely results of the action. For example, if the Treaty of Versailles had not imposed such harsh conditions on Germany, it is unlikely that World War II would have occurred (war was an 'unintended consequence'). However, it would be incorrect to call the movie Schindler's List an 'unintended consequence' of the Treaty of Versailles.
Unintended consequences can be classed into roughly three types:
- a positive unexpected benefit, usually referred to as serendipity or a windfall
- a potential source of problems, according to Murphy's law used in Systems engineering
- a negative or a perverse effect, which is the opposite result of what is intended
Discussions of unintended consequences usually refer to the third situation of perverse results. This situation often arises because a policy has a Perverse incentive and causes actions contary to what is desired.
 The Law of Unintended Consequences
The Law of Unintended Consequences holds that almost all human actions have at least one unintended consequence. In other words, each cause has more than one effect, including unforeseen effects. The idea dates to the Scottish Enlightenment, which influenced interdisciplinary leaders such as Thomas Jefferson and Matthew F. Maury who had the same tutor - Reverend James Maury.
In the twentieth century, sociologist Robert K. Merton once again popularized the concept, sometimes referred to as the Law of Unforeseen Consequences. Merton (1936) spoke of the "unanticipated consequences" of "purposive social action", emphasizing that his term "purposive action… [is exclusively] concerned with 'conduct' as distinct from 'behavior.' That is, with action which involves motives and consequently a choice between various alternatives" (p.895).
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 causes of unanticipated consequences:
- Ignorance (It is impossible to anticipate everything)
- Error (Incomplete 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)
Merton is also said to have stated that "no blanket statement categorically affirming or denying the practical feasibility of all social planning is warranted."
Of course, unintended consequences are common in everyday life, but many impact the greater society.
Examples of 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.
- The wartime practice of sinking ships in shallow waters has created some artificial coral reefs.
- Controversial research carried out by John J. Donohue and Steven Levitt and published in the Quarterly Journal of Economics suggests that legalized abortion in the United States has accounted for as much as 50% of the drop in national crime rates. As evidence, Donohue and Levitt cite the fact that states which legalized abortion before Roe v. Wade saw correspondingly earlier drops in crime, and that 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."
- Also controversially, it has been suggested that legalized abortion has led to fewer so-called 'crack babies'—children born with a drug dependency due to their mothers' drug use while pregnant. The availability of legal abortion makes it more likely that a drug-addicted mother will abort a fetus rendered unhealthy by her drug use, even if this is not a primary reason for her choice to abort. (Note: the theory that fetuses exposed to crack cocaine would become people prone to violence, crime or addiction has been proven false. Crack babies perform as well as their age cohorts and show no additional tendency to violence, crime or addiction. However, babies with fetal alcohol syndrome, exposed to alcohol in the first trimester, do show significant mental delay, and tendency to violence, crime, and drug abuse.)
- 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.
Examples of Peverse Results:
- The introduction of rabbits into Australia for sport led to an explosive growth in the rabbit population; rabbits became a major feral pest in Australia.
- Most economists believe that minimum wage laws increase the unemployment rate among low wage workers.
- Driven by concern for the increasing number of cyclist’s head injuries, the State of Victoria (Australia) legislated to make safety helmets mandatory for all bicycle riders in 1990. Whilst the expected significant reduction in the absolute number of head injuries was certainly observed, there was also a concomitant, entirely unexpected reduction in the number of juvenile cyclists. Research by Vulcan et al. found that the reduction in the number of juvenile cyclists was entirely due to the fact that wearing a bicycle helmet was not considered to be "cool".
- "Prohibition" in the 1920s U.S., originally intended 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. When Prohibition was repealed, the brewing industry was then concentrated in a few major brewers who were able to ride it out. Sixty years later, the "War on Drugs," intended to suppress the illegal drug trade, has likewise driven many small-time drug dealers out of business and consolidated the hold of organized drug cartels over the illegal drug industry. Additionally, it has led to the existence of street drugs of unknown strength and contamination; at least some drug-related (and particularly opiate-related) deaths are caused by accidental overdosing on drugs which a dealer neglected to dilute to the usual extent.
- In CIA jargon, "blowback" describes the unintended, even undesirable consequences of covert operations. Examples include:
- Attempts by governments to reduce rent by introducing rent control has led to the unintended consequence of housing shortages and reduction in housing quality, increased difficulty for less desirable renters to obtain or retain housing and even the creation of slums—areas where rental property is allowed to run down until it becomes uninhabitable.
- Controversially, it has been argued that stronger gun control has caused places such as Washington DC and New Jersey to experience unexpected increases in crime. One possible reason is that the enactment of gun control laws leave citizens vulnerable to criminals who do not respect the prohibitions on gun ownership, thereby making crime a much safer occupation. Conversely, places such as Switzerland and Vermont are cited as examples of places where weapons are common (and, importantly, equally distributed), yet the crime rates are extraordinarily low.
 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).<ref>Urban-wetland example showing unintended consequences (secondary and subsequent) of land-use zoning and flooding: Hazard Tree Analysis</ref>
 Purposeful gaming to achieve unintended consequences
Another more restrictive use of unintended consequence is that it occurs when a mechanism that has been installed in the world with the intention of producing one result is used to produce a different (and often conflicting) result. The notion of "gaming the system" illustrates the idea of an unintended consequence. One "games a system" (for example, the tax code) when one acts in such a way that one gains tax advantages by exploiting a tax rule that was intended for some other purpose. Similarly, 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 intent to "game the system" distinguishes this interpretation of unintended consequence from the more common interpretation of unintended consequence as a result of simple historical contingency. See the Museum of Unintended Consequences for more examples.
 See also
- Futures techniques
- Hutber's law
- Moral hazard
- Murphy's law
- Perverse effects of vaccination
- Perverse incentive
- Placebo (origins of technical term)
- Regression testing
- Side effect
- Streisand effect
- Unforeseen effects of species introduction
 External links
- 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.fr:Effet pervers