Consumption externalities
When the social cost/benefits exceed the private costs/benefits.
If social benefits exceed private benefits then it is a positive consumption externality
If social costs exceed private costs it is negative
Externality/spillover effect
The difference between private and social costs/benefits.
Marginal Social costs/ benefits
Societies costs and benefits from an additional unit
Marginal private cost/benefit
the private costs and benefits from an additional unit
Production externalities
When social costs of production are different to private costs.
MSC > MPC = Negative
MPC > MSC = Positive
Social cost / benefit
The cost / benefit to the whole of society