What is the difference between positive and negative externalities?

Answer 1

• A negative externality (sometimes referred to as an "external cost") exists when an economic actor produces an economic cost but does not fully pay that cost. A well-known example is the manufacturing firm that dumpspollutants in a river, decreasing water quality downstream.
• A positive externality (sometimes referred to as an "external benefit") exists when an economic actor produces an economic benefit but does not reap the full reward from that benefit. Positive externalities are less well-known, but can be vitally important to individual and societal well-being. A landowner, for example, by choosing not to develop her land might preserve awater recharge source for an aquifer shared by the entire local community. Other examples are parents who, out of love for their children, raise them to become decent people (rather than violent criminals). In so doing they also create benefits for society at large. Similarly, when one person gets vaccinated against a communicable disease, she not only protects herself, but also others around her, from the disease's spread. In both cases there are social benefits from individual actions: Well-educated, productive citizens are an asset to the community as well as to their own families; and disease control reduces risks for everyone.