Unintended consequences

**Unintended consequences** are the surprising results of an action or decision.

When an  is not  or , the situation at the end of a process may be different from what was .  In other words, purposeful action may create s which are: 
* Not intended (unintended)
* Not expected (unanticipated) 
* Not predicted (unforeseen)

This concept is one of the building blocks of economics.  The term was coined and popularised in the 20th century. Its use has expanded into a range of contexts.

## History
The idea of unintended consequences dates back at least to the 18th century, when Adam Smith wrote about men who are "led by an invisible hand to promote an end which was no part of his invention".

American sociologist Robert K. Merton invented the phrase in 1936.

## Types 
There are three types of unintended consequences:
* A positive, unexpected good effect (also described as )
* A negative, unexpected bad effect in addition to what was expected
* A strange, unpredicted effect which is outside the scope or opposite to what was intended

## Causes 
Possible causes of unanticipated consequences include

;Ignorance
* In other words, it is impossible to anticipate everything, and this leads to an analysis which is not detailed enough.

;Error
* In other words, there is an incorrect or mistaken analysis.  For example, error might result from following a process or procedure which worked in the past but which does not work well enough or not at all in a new situation.

; Immediate interest
* In other words, the focus on short-term goals may be viewed as more important than long-term interests.

;Basic values
* In other words, there may be factors which require or prohibit certain actions regardless of the long-term results.

## Select examples 
There are examples and kinds of unanticipated consequences:

;Unexpected and good
*Aspirin is a pain reliever.  Among other things, aspirin affects the blood's ability to clot.  An unintended consequence is that aspirin is sometimes good for people with heart problems.

; Unexpected and bad 
* Rabbits were introduced in Australia and New Zealand; but without any natural enemies to slow the growth in numbers, there was an unanticipated consequence. There was a problem of too many rabbits in both countries.

; Unexpected and worse
* In India, the southern provinces had the problem of too many snakes.  The government tried to solve the problem by paying for dead cobras.  This was intended to bring down the number of cobras. Instead, it led to the breeding of cobras.  When the government stopped paying for dead cobras, the snakes were released—and the problem was worse than before the government tried to do something about it.

### Cheaper and easier travel 
Cheaper travel, mostly in the form of air transport, is hugely beneficial to the economy by increasing tourism into a country. It accounts for 30% of the world's trade of services, and 6% of overall exports of goods and services. It also creates opportunities for employment in the services needed for tourism.

With increased tourism comes a variety of unlooked-for problems, such as increased illegal immigration. Perhaps even more serious is that returning tourists may bring back parasites and diseases which are not usual in the home country. Furthermore, many of these organisms are now resistant to most treatment.

## Related pages 
* The road to hell is paved with good intentions
* Perverse incentive
* Moral hazard

## References