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 the American sociologist Robert K. Merton. Unintended consequences can be grouped into three types:
Unexpected benefit: an unexpected benefit (also known as serendipity). Unexpected drawback: an unexpected detrimental effect, occurring in addition to the desired one. For example, while irrigation schemes may provide farmers with water for agriculture, they may also lead to a rise in the prevalence of waterborne diseases such as schistosomiasis. Perverse result: an effect contrary to what was originally intended. For example, while irrigation schemes intended to increase yields may improve water availability and increase agricultural yields in the short term, they might also lead to soil salination and the depletion of freshwater resources, decreasing yields in the long term.
History
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.
Adam Smith The idea was also discussed by Adam Smith, the Scottish Enlightenment, and consequentialism (judging by results).
The invisible hand theorem is an example of the unintended consequences of agents acting in their self-interest. As Andrew S. Skinner puts it:"The individual undertaker (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."
Marx and Engels Influenced by 19th century positivism and Charles Darwin's 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. 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:
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. 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) 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.» This social conflicts would happen as a result of a competitive society, and also lead society to sabotage itself and prevent historical progress. Thus, historical progress (in Marxist terms) should eliminate these conflicts and make unintended consequences predictable.
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.
Carl Menger In "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 good can have ramifications beyond that good. Menger wrote:
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. [...]Thus quinine would cease to be a good if the 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.
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