what is the difference between negative and positive externalities
Externality Voluntary exchange is by definition mutually beneficial to both business parties involved, because the parties would not agree to undertake it if either thought it detrimental to their interests. However, a transaction can cause effects on third parties without their knowledge or consent. From the perspective of those affected, these effects may be negative (pollution from a nearby factory), or positive (honey bees kept for honey that also pollinate neighboring crops). Neoclassical welfare economics asserts that, under plausible conditions, the existence of externalities will result in outcomes that are not socially optimal. Those who suffer from external costs do so involuntarily, whereas those who enjoy external benefits do so at no cost.
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]