an external cost or external benefit is also known as
Externality Two British economists are credited with having initiated the formal study of externalities, or "spillover effects": Henry Sidgwick (1838–1900) is credited with first articulating, and Arthur C. Pigou (1877–1959) is credited with formalizing the concept of externalities.[5]
Competition (economics) The competitive process in a market economy exerts a sort of pressure that tends to move resources to where they are most needed, and to where they can be used most efficiently for the economy as a whole. For the competitive process to work however, it is "important that prices accurately signal costs and benefits." Where externalities occur, or monopolistic or oligopolistic conditions persist, or for the provision of certain goods such as public goods, the pressure of the competitive process is reduced.[2]