A cost or benefit arising from any activity which does not accrue to the person or organization carrying out the activity. Negative externalities cause damage to people, firms, or the environment, for example by radiation, river or air pollution, or noise, which does not have to be paid for by those carrying out the activity. Positive externalities are effects of an activity which are pleasant or profitable but for which no price can be charged, for example fertilization of fruit trees by bees, or the public’s enjoyment of views of private buildings or gardens. Externalities may be technological or pecuniary. Technological externalities affect others in non-market ways, for example by polluting their water supply; they create a prima facie case for intervention in the interests of efficiency. Pecuniary externalities mean that the effects occur through the market: for example, the emergence of a new industry may raise labour costs for other employers, or reduce the value of their capital by capturing their customers. Pecuniary externalities do not result in Pareto inefficiency so there is no case for intervention, except possibly on grounds of income distribution. See also compensation for externalities; consumption externality; internalizing externalities; network externality; production externality.