What is the externalities n which way it give the benefits to society?

Question

What is the externalities n which way it give the benefits to society?

Answer 1

it can be -ve or +ve types.  -ve will cost society more.   eg factory in china located upstream river.  it discharges its waste into the yellow river.  the river gets polluted and villages downstream cant use it and their livelihood / lifestyle are affected.  the factory must realize the externalities involved and with an ethical consideration do something to correct  the imbalance. in old sch of thought,  factory is not responsible.  but now corporate social responsibility is paramount.  

another one is flu vaccine.  everyone shld take it. if u catch flu, your productivity is affected.  u infect others and a whole company can be affected.  by taking flu shots, the externality is +ve