Can You Explain The Term Of Externalities?

In market economies, the externalities or external effects also distort the situation of efficient allocation of resources and maximization of output when we find the divergences between private and social benefits. The externalities may be concerned with the production as well as with consumption.

The production externalities are concerned with production activities which are carried on without considering their side effects on the others. For example, if a producer installs a chemical plant and maximizes his output/profits, but he does not make any compensation to those persons who dwell near the plant and have to face the polluted atmosphere. In this way a divergence between private benefit and social benefit may emerge a situation against the Pareto's optimality.

Again, the investment in a certain line may increase the profit of another investor whose project is complementary to it. In this situation, social benefits may exceed the private benefit. The market mechanism fails to entertain and evaluate these external effects.
Regarding consumption externalities, the external renovation of a house by an owner may lead to enhance the beauty of the whole street. While the non existence of a road etc, to a particular locality may lead to reduce the value of the locality.

Private cost and benefit calculations, which are the basis of market allocation, do not provide a sound basis in decision making from the social point of view. Thus the price is not a reliable signal in respect of all allocation of resources.