Negative externalities of consumption
Syllabus: Explain that demerit goods are goods whose consumption creates external costs.
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How to draw the negative externality of Consumption Diagram
1. Draw and label the Price and Quantity axes
2. Draw the downward sloping Marginal Private Benefit (demand) curve MPB
3. Draw the upward sloping Marginal Private Cost curve MPC (it is just MC in the diagram above) because there are no production externailities)
4. Indicate the equilibrium price and quantity level (NB This is what market forces of supply and demand lead to) In other words resources are allocated to this level of output (Qm) and this price (Pm)
5. Draw in the Marginal Social Benefit (MSB) curve, which must be lower than MPB because it now also includes negative external benefits so overall benefits are lower (NB Consumption considerations affect benefits)
6. Indicate the Price (Ps) and Quantity (Qs) that would be the equilibrium if full social benefits were to be included in the decision making processes
7. Compare the market quantity with the Social Optimum and you can see more is consumed (more resources allocated) than society as a whole wants or needs (Qm>Qs)
Using the same procedure can you now draw the diagram for Positive Externalities of consumption