Today

Review table on monopolistic competitionExternalities—Ch. 30

Table 1a

Perfect Comp Monopolistic Competition

Monopoly

Firms are price takers Firms are price makers

Firms are price makers

Choose q where P=MC Choose q where MR=MC

Choose q where MR=MC

In SR, P AVC in order to produce.

In SR, P AVC in order to produce.

In SR, P AVC in order to produce.

In LR, P ATC in order to produce.

In LR, P ATC in order to produce

In LR, P ATC in order to produce.

Firms face perfectly elastic demand for their product.

Firms face downward-sloping market demand.

Firms face downward-sloping market demand.

Table 1b

Perfect Comp Monopolistic Competition

Monopoly

No profits or losses in LR

No profits or losses in LR

May have profits in LR

No barriers to entry or exit

Barriers to Entry Barriers to Entry

Firms produce at lowest possible LRAC

Produce on downward-sloping portion of LRAC

May or may not produce at lowest possible LRAC

In LR equilibrium, P = MC

In LR equilibrium, P > MC

In LR equilibrium, P > MC

Table 1c

Perfect Comp Monopolistic Competition

Monopoly

No need for advertising, goods are homogeneous

Advertising may increase demand for product

Advertising may increase demand for product

Brand name is unimportant to consumers

Brand name is often very important

Only one brand to choose from

Externality

When an individual course of action affects others beyond the amount considered by that individual.

Negative externality

The individual course of action imposes costs on others.

Example: Bob’s smoking

Costs to Bob Cost of cigarettes Cost to own health Cost of keeping home and clothes clean

Costs to others from Bob’s smoking Health costs from second-hand smoke Cost of cleaning home, clothes Increased price of health insurance due to inclusion

of smokers in group rates.

Social Costs

The social cost of the activity is the private cost plus the external cost.

The social cost of one person smoking includes the costs to the smoker plus the costs to others.

Social Benefits

The social benefits are equal to the private benefits plus any external benefits.

Assume no external benefits from Bob smoking. Note: if there are external benefits, that is a

positive externality, see below.

Then the social benefits of Bob smoking are just the private benefits that Bob gets.

Marg.Ext. Cost

Costs versus Benefits$/Cigarette

Marginal Private Cost (to Bob)

Marginal Social Cost (to Bob & to others)

Marginal Benefit (Bob)

How much will Bob smoke?How much is optimal?

Bob’s choice versus society’s

Cigarettes/day

Marginal Private Cost

Marginal Social Cost

Marginal Benefit How can society get Bob (& others) to smoke less?

Bob’s choice

Optimalfor society

Social costs exceed benefits.

$/Cigarette

A Tax to Correct Negative Externalities

Society wants Bob to internalize the external costs of his smoking.

One way to do that is to tax cigarettes.The amount of the tax per cigarette should

equal the costs to others from Bob’s smoking.

Tax per cig.

A Tax on Cigarettes

Cigarettes/day

Marginal Private Cost

Marginal Social Cost =Marg. Private Cost + taxMarg. Private Cost + tax

Marginal Benefit

Use a tax to force Bob to pay the full costs of his smoking.

Bob’s choice if

taxed

Optimal

$/Cigarette

Pollution as a Negative Externality

Industrial production often creates pollution of air or water as a by-product.

Public policy options for dealing with pollution Ban pollution Tax pollution Establish maximum rates of pollution per firm Issue a limited number of permits to pollute, allow

them to be traded. (Used for CO2 in US)

The Tragedy of the Commons

Why is the copier always out of paper or in a paper jam?

“The Commons”

Historically, refers to common grazing land for a town.

In economics, refers to any situation in which a resource is used by many people, none of whom owns the resource.

What happened in “The Commons”?

The private cost of grazing your sheep in the commons was zero.

The social cost wasn’t, because once your sheep ate the grass, it wasn’t there for the next farmer.

The commons were routinely over-grazed, because nobody had an incentive to make sure the grass had time to grow back.

Current “Tragedies”

Fishing in the ocean There are no property rights to fishing grounds in

international waters. Fisherman have no incentive to let the population recover.

The shared copier The cost of fixing the paper jam is higher than the

benefits one person expects to get out it. Tendency to move on to another machine, or wait

until someone else fixes the problem.

Other Tragedies

Air Quality We drive our cars without regard to the marginal cost

to society of the air pollution. Gasoline taxes help.

Use of Outer Space Without some sort of controls, likely to see so much

debris and so many satellites that the use of space is impaired.

Public restrooms

Positive externality:

The individual course of action imposes benefits on others.

The social benefit of an activity is greater than the private benefit.

Examples of Positive Ext.

Education: Makes people better citizens. These benefits are in addition to the private benefits.

Attractive architecture, landscaping, etc. at your house increases the value of the neighbors’ houses.

Vaccinations: When one person is vaccinated, it helps the rest of us because we are less likely to catch the disease.

The Role of the Government & Externalities

Governments can use taxes to discourage activities with negative externalities.

They can use subsidies to encourage activities with positive externalities.

Government Regulation

Planning commissions or architectural review boards are used to create positive externalities rather than negative ones.

Commercial activities tend to be zoned separately from residential neighborhoods.

Property owners may be required to preserve historic buildings or to complement existing buildings.

Coming Up

Review for third midterm exam

Group Work-Externalities

List 3 examples of negative externalities (not already mentioned in class). How does society address each?

List 3 examples of positive externalities (not already mentioned in class). How does society address each?

Write out your answers.