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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Lecture 11:Externalities and Public Goods
November 10, 2015
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Overview
Course Administration
Positive and Negative Externalities
Fixing Externalities
Defining Public Goods
Optimal Provision of Public Goods
Private Provision of Public Goods
Public Provision of Public Goods
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Course Administration
1. Bookstore website says reading packet needed for next week isavailable
2. Problem Set 10 is posted, problem set 8 answers posted
3. Elasticity paper: voluntary classmate feedback• Post paper by Nov. 17 8 pm to Blackboard discussion board
called “elasticity paper draft”• Put last name at beginning of file name• You’ll need to return comments on 2 to 3 papers by 8 pm
12/22 (Sunday) – and you could make alternate arrangementswith your group
• I’ll assign groups randomly after papers are posted• Suggestions?
4. Office hours extended: Wednesdays 10 am to 1 pm
5. Last class: probably 1/2 class asymmetric information, 1/2review
6. Questions?
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Ripped from the Headlines
Next Week
Afternoon
Finder Presenter
Lily Robin Carly Evans
Evening
Finder Presenter
Amber Ebarb Jenny Lewis
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Externality Definition
Externality ≡ cost or benefit accruing to party not involved ineconomic transaction
• Positive externality ≡ benefit accruing to party not involved ineconomic transaction
• Negative externality ≡ cost accruing to party not involved ineconomic transaction
Examples, please.
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Externality Definition
Externality ≡ cost or benefit accruing to party not involved ineconomic transaction
• Positive externality ≡ benefit accruing to party not involved ineconomic transaction
• Negative externality ≡ cost accruing to party not involved ineconomic transaction
Examples, please.
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Externality Definition
Externality ≡ cost or benefit accruing to party not involved ineconomic transaction
• Positive externality ≡ benefit accruing to party not involved ineconomic transaction
• Negative externality ≡ cost accruing to party not involved ineconomic transaction
Examples, please.
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Externality Definition
Externality ≡ cost or benefit accruing to party not involved ineconomic transaction
• Positive externality ≡ benefit accruing to party not involved ineconomic transaction
• Negative externality ≡ cost accruing to party not involved ineconomic transaction
Examples, please.
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
In a Market Without Externalities
P
D
Q
S
• If private demand = privatemarginal benefit = socialmarginal benefit
• And Private supply =private marginal cost =social marginal cost
• Then market equilibriummaximizes social welfare,which is total surplus
• Provides goods to consumerat lowest possible cost
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
In a Market With Externalities
Assume a negative externality
• =⇒ Social marginal cost 6= private marginal cost
• =⇒ Social marginal cost = Private marginal cost + externalmarginal cost
Assume a positive externality
• =⇒ Social marginal benefit 6= private marginal benefit
• =⇒ Social marginal benefit = Private marginal benefit +external marginal benefit
What does this mean for the relationship between marketequilibrium PMKT and QMKT and socially optimal PSOC andQSOC?
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
In a Market With Externalities
Assume a negative externality
• =⇒ Social marginal cost 6= private marginal cost
• =⇒ Social marginal cost = Private marginal cost + externalmarginal cost
Assume a positive externality
• =⇒ Social marginal benefit 6= private marginal benefit
• =⇒ Social marginal benefit = Private marginal benefit +external marginal benefit
What does this mean for the relationship between marketequilibrium PMKT and QMKT and socially optimal PSOC andQSOC?
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
In a Market With Externalities
Assume a negative externality
• =⇒ Social marginal cost 6= private marginal cost
• =⇒ Social marginal cost = Private marginal cost + externalmarginal cost
Assume a positive externality
• =⇒ Social marginal benefit 6= private marginal benefit
• =⇒ Social marginal benefit = Private marginal benefit +external marginal benefit
What does this mean for the relationship between marketequilibrium PMKT and QMKT and socially optimal PSOC andQSOC?
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
What Does a Negative Externality Do to Market Supply?Where Are the Private Market P and Q?
P
D
Q
S = MC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
What Does a Negative Externality Do to Market Supply?Where is the Social Marginal Cost?
P
D
Q
S = MC
QMKT
PMKT
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
What Does a Negative Externality Do to Market Supply?What are the Socially Optimal P and Q?
P
D
Q
S = MC + EMC
S = MC
QMKT
PMKT
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
What Does a Negative Externality Do to Market Supply?What is the Vertical Distance Between the Supply Curves?
P
D
Q
S = MC + EMC
S = MC
QMKTQSOC
PMKT
PSOC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
What Does a Negative Externality Do to Market Supply?Where is the Deadweight Loss?
P
D
Q
S = MC + EMC
S = MCEMC
QMKTQSOC
PMKT
PSOC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
What Does a Negative Externality Do to Market Supply?Too Much Production, at Too Low a Price
P
D
Q
S = MC + EMC
S = MCEMC
QMKTQSOC
PMKT
PSOC
DWL
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Positive ExternalitiesWhere Are Market Equilibrium P and Q?
P
Q
D = PMB
S
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Positive ExternalitiesWhere is the Social Marginal Benefit Curve?
P
Q
D = PMB
S
QMKT
PMKT
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Positive ExternalitiesWhat are the Socially Optimal P and Q?
P
Q
D = PMB
S
QMKT
PMKT D = PMB + EMB
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Positive ExternalitiesWhat is the Vertical Difference Between the Demand Curves?
P
Q
D = PMB
S
QMKT QSOC
PMKT
PSOCD = PMB + EMB
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Positive ExternalitiesWhere is the Deadweight Loss?
P
Q
D = PMB
SEMB
QMKT QSOC
PMKT
PSOCD = PMB + EMB
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Positive ExternalitiesToo Little Production, at Too High a Price
P
Q
D = PMB
SEMB
QMKT QSOC
PMKT
PSOCD = PMB + EMB
DWL
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Try It Yourself: Negative Externalities
Suppose that leather is sold in a perfectly competitive industry.The industry short-run supply curve (marginal cost curve) isP = MC = 3Q, where Q is measured in millions of hides per year.The demand for leather hides is given by Q = 60/7− P/7.
1. Find the equilibrium market price and quantity.
2. Suppose that the leather tanning releases bad stuff intowaterways. The external marginal cost is $4/hide. Calculatethe socially optimal level of output and price for the tanningindustry.
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
What is the Right Level of Production with NegativeExternalities?
• Efficient level of production ≡ level of production necessary toproduce the efficient quantity of the good tied to theexternality
• Assume that there is a marginal cost of production (= privatecost + external cost)
• Assume that there is a marginal benefit of production (=marginal cost of abatement)
• What level of production is optimal?
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Optimal Provision of a Good with a Negative Externality
Whyis POLL∗ 6= 0?
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Getting to the Socially Optimal P and Q
Three methods
1. Change prices
2. Change quantities
3. Tradeable permits
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
1. Using Taxes and Subsidies to Return to the EfficientPoint
• Suppose we know the external marginal cost
• Charge a tax equal to the external marginal cost
• This returns us to the socially optimal equilibrium outcome
• Called a Pigouvian tax
• Requires that you (the policymaker) know the cost exactly
• Can redistribute tax revenues to those harmed by policy
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
To Be Clear
Before tax
• private marginal cost = MC
• social marginal cost = MC + EMC
After tax, T = EMC
• private marginal cost = MC + T
• social marginal cost = MC + EMC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
To Be Clear
Before tax
• private marginal cost = MC
• social marginal cost = MC + EMC
After tax, T = EMC
• private marginal cost = MC + T
• social marginal cost = MC + EMC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
1a. Correcting for a Negative ExternalityPrivate and Social Supply Before a Tax
P
D
Q
S = MCEMC
QMKTQSOC
PMKT
PSOC
S = MC + EMC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
1a. Correcting for a Negative ExternalityAfter the Tax, Private Supply = Social Supply
P
D
Q
S = MC + EMC = MC + T
S = MCEMC = T
QMKT
PMKT
QSOC
PSOC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
1b. Correcting for a Positive ExternalityPrivate and Social Demand Before a Subsidy
P
Q
D = PMB
SEMB
QMKT QSOC
PMKT
PSOCD = PMB + EMB
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
1b. Correcting for a Positive ExternalityAfter the Subsidy, Private Demand = Social Demand
P
Q
D = PMB
SEMB= Sub
QMKT
PMKT D = PMB + EMB= PMB + Sub
QSOC
PSOC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
2. Using a Quota to Get to Efficient PointPrivate and Social Supply Before a Quota
P
D
Q
S = MC + EMC
S = MCEMC
QMKT
PMKT
QSOC
PSOC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
2. Using a Quota to Get to Efficient PointWith a Quota
P
D
Q
S = MC + EMC
S = MCEMC
QMKT
PMKT
S = MC w/ quota
QSOC
PSOC
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
The Trouble with Using Quotas
1. May be hard to know optimal market output level
2. Even if you know the optimal market output, policy mustassign quotas by firm. Ideally, you’d assign quotas by cost ofreduction, but you’d need to know firm-specific costs.
3. All costs and benefits are borne by market participants; no taxrevenues to redistribute
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
The Trouble with Using Quotas
1. May be hard to know optimal market output level
2. Even if you know the optimal market output, policy mustassign quotas by firm. Ideally, you’d assign quotas by cost ofreduction, but you’d need to know firm-specific costs.
3. All costs and benefits are borne by market participants; no taxrevenues to redistribute
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
3. Tradeable Permits
• The government decides how much negative activity (orpositive activity) to allow
• It makes permits to allow that much activity
• It distributes permits to anybody (firms, you)• The choice of distribution method determines winners and
losers!
• Permits trade
Why is this superior in terms of getting to the equilibriumoutcome?
• Government doesn’t need to know anything about firms’ coststructures
• Firms with lowest cost of reducing activity will undertake it
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
3. Tradeable Permits
• The government decides how much negative activity (orpositive activity) to allow
• It makes permits to allow that much activity
• It distributes permits to anybody (firms, you)• The choice of distribution method determines winners and
losers!
• Permits trade
Why is this superior in terms of getting to the equilibriumoutcome?
• Government doesn’t need to know anything about firms’ coststructures
• Firms with lowest cost of reducing activity will undertake it
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
3. Tradeable Permits
• The government decides how much negative activity (orpositive activity) to allow
• It makes permits to allow that much activity
• It distributes permits to anybody (firms, you)• The choice of distribution method determines winners and
losers!
• Permits trade
Why is this superior in terms of getting to the equilibriumoutcome?
• Government doesn’t need to know anything about firms’ coststructures
• Firms with lowest cost of reducing activity will undertake it
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Defining Public Goods
Public goods are both non-rival and non-excludable
• Non-rival ≡ goods where your consumption does not impactmy consumption
• Non-excludable ≡ goods from which consumption cannot beexcluded
Pure public goods are rare: national defense, perhaps air forbreathing.Public goods are not necessarily publicly provided goods.
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Defining Public Goods
Public goods are both non-rival and non-excludable
• Non-rival ≡ goods where your consumption does not impactmy consumption
• Non-excludable ≡ goods from which consumption cannot beexcluded
Pure public goods are rare:
national defense, perhaps air forbreathing.Public goods are not necessarily publicly provided goods.
![Page 45: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/45.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Defining Public Goods
Public goods are both non-rival and non-excludable
• Non-rival ≡ goods where your consumption does not impactmy consumption
• Non-excludable ≡ goods from which consumption cannot beexcluded
Pure public goods are rare: national defense, perhaps air forbreathing.
Public goods are not necessarily publicly provided goods.
![Page 46: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/46.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Defining Public Goods
Public goods are both non-rival and non-excludable
• Non-rival ≡ goods where your consumption does not impactmy consumption
• Non-excludable ≡ goods from which consumption cannot beexcluded
Pure public goods are rare: national defense, perhaps air forbreathing.Public goods are not necessarily publicly provided goods.
![Page 47: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/47.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Public Good Typology
Rival Non-Rival
Excludable Private good Club goodNon-Excludable Common resource Pure public good
With your neighbors: examples of each type. Can substitute alocal public good for the “pure public good.”
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Optimal Provision of Private Goods
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Using Algebra To Do This
Suppose we have two demand curves
• QJoe = 5− 0.05P
• QJack = 13− 0.25P
This is a piece-wise linear function. What are the pieces?
• At P > $52, Jack doesn’t want any more
• At P > $100, Joe doesn’t want any more
We write this as
QM =
{18− 0.3P if 0 < P < 52
5− 0.05P if P > 52
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Adding Private Good Demand
• For private goods, we add up Q at a given price, P
• How many oranges do people want to buy if the price is $6?
• Mechanically, add Q = f (P)
Why doesn’t this work for public goods?
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Adding Private Good Demand
• For private goods, we add up Q at a given price, P
• How many oranges do people want to buy if the price is $6?
• Mechanically, add Q = f (P)
Why doesn’t this work for public goods?
![Page 52: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/52.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Optimal Provision of Public Goods?How Much Are Mr. 1 and Mr. 2 Willing to Pay for Q2 of Fireworks?
Q
P1
P2
Q
P1,2
P2,2
QQ2
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Optimal Provision of Public Goods?To See Demand at Q2
Q
P1
P2
Q
P1,2
P2,2
P1+P2
P1,2+P2,2
QQ2
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Optimal Provision of Public Goods?Market Demand for Public Goods
Q
P1
P2
Q
P1,2
P2,2
P1+P2
P1,2+P2,2
QQ2
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Optimal Provision of Public Goods?Equilibrium Provision of Public Goods
Q
P1
P2
Q
P1,2
P2,2
P1+P2
P1,2+P2,2
QQ2
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Adding Market Demand for Public Goods in Math
• For public goods, we add up P at a given quantity, Q
• For 300 fireworks, how much is everyone willing to pay?
• Mechanically, add P = g(Q)
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Level of Private Provision of Public Goods
• Suppose• Mr. 1 likes 6 units of the public good• Mr. 2 likes 5 units of the public good• Mr. 1 purchases 6 units• What is Mr. 2’s best response?
• This is known as the “free rider problem” ≡ failure tocontribute to public good
• =⇒ in general, private markets underprovide public goods
• Don’t blame the producer!
Even goods that a whole group wants and is willing to pay for maynot be provided.
![Page 58: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/58.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Level of Private Provision of Public Goods
• Suppose• Mr. 1 likes 6 units of the public good• Mr. 2 likes 5 units of the public good• Mr. 1 purchases 6 units• What is Mr. 2’s best response?
• This is known as the “free rider problem” ≡ failure tocontribute to public good
• =⇒ in general, private markets underprovide public goods
• Don’t blame the producer!
Even goods that a whole group wants and is willing to pay for maynot be provided.
![Page 59: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/59.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Level of Private Provision of Public Goods
• Suppose• Mr. 1 likes 6 units of the public good• Mr. 2 likes 5 units of the public good• Mr. 1 purchases 6 units• What is Mr. 2’s best response?
• This is known as the “free rider problem” ≡ failure tocontribute to public good
• =⇒ in general, private markets underprovide public goods
• Don’t blame the producer!
Even goods that a whole group wants and is willing to pay for maynot be provided.
![Page 60: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/60.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Level of Private Provision of Public Goods
• Suppose• Mr. 1 likes 6 units of the public good• Mr. 2 likes 5 units of the public good• Mr. 1 purchases 6 units• What is Mr. 2’s best response?
• This is known as the “free rider problem” ≡ failure tocontribute to public good
• =⇒ in general, private markets underprovide public goods
• Don’t blame the producer!
Even goods that a whole group wants and is willing to pay for maynot be provided.
![Page 61: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/61.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Example: Private Provision of Public Goods
• Property owners in a neighborhood agree to levy taxes onthemselves
• Motivation: owners feel that public services are substandard
• Use tax revenues to privately provide services, such ascleaning, marketing and security
• Generally regarded as being successful – my research showslowered crime in City of LA
• Overcome the free-rider problem with mandatory contribution
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
When Does Private Market Provide Some Public Goods?
• The smaller the group, the more likely the provision
• When one, or a few, members care a lot – we see this in BIDs
• Altruism
• Warm glow
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Can the Government Do Better?
Due to the failure in the private market, one solution is forgovernment to provide public goods.
What do you think theproblems are with this?
• Free-rider problem again: optimal amount of public goods issum of P given Q
• Asking citizens to reveal their true demand is called “Lindahlpricing”
• Yields optimal quantity of public goods• Consumers might not know their demand (do you know your
demand for missiles?)• And consumers have an incentive to underestimate
• Government provision “crowds out” private provision• Before the government firework show, you might have bought
some of your own. Now you do not. Other examples?
• Costs and benefits hard for government to measure
![Page 64: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/64.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Can the Government Do Better?
Due to the failure in the private market, one solution is forgovernment to provide public goods. What do you think theproblems are with this?
• Free-rider problem again: optimal amount of public goods issum of P given Q
• Asking citizens to reveal their true demand is called “Lindahlpricing”
• Yields optimal quantity of public goods• Consumers might not know their demand (do you know your
demand for missiles?)• And consumers have an incentive to underestimate
• Government provision “crowds out” private provision• Before the government firework show, you might have bought
some of your own. Now you do not. Other examples?
• Costs and benefits hard for government to measure
![Page 65: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/65.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Can the Government Do Better?
Due to the failure in the private market, one solution is forgovernment to provide public goods. What do you think theproblems are with this?
• Free-rider problem again: optimal amount of public goods issum of P given Q
• Asking citizens to reveal their true demand is called “Lindahlpricing”
• Yields optimal quantity of public goods• Consumers might not know their demand (do you know your
demand for missiles?)• And consumers have an incentive to underestimate
• Government provision “crowds out” private provision• Before the government firework show, you might have bought
some of your own. Now you do not. Other examples?
• Costs and benefits hard for government to measure
![Page 66: Lecture 11: Externalities and Public Goodslfbrooks/leahweb/teaching/pppa6085/2015/lecture... · AdminExternalitiesFix Ext.Public Goods Q PG Private PGPublic PG Course Administration](https://reader030.vdocuments.us/reader030/viewer/2022040904/5e76ec3667514c410c745ba6/html5/thumbnails/66.jpg)
Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Recap of Today
• Externalities• Definitions, positive and negative• Possible corrections
• Public goods• Definition• Equilibrium market provision• Adding up demand for public goods
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Next Class
• Turn in Problem Set 10
• Taxes!
• Gruber 18 and 19
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Admin Externalities Fix Ext. Public Goods Q∗PG Private PG Public PG
Problem 1
1. Equilibrium price and quantity. Find equilibrium P and Q by settingQS = QD (or PS = PD). To set the curves equal, we need to startby finding inverse demand. If Q = 60/7− P/7, then P = 60− 7Q.Set 3Q = 60− 7Q, or 10Q = 60, which implies Q∗
market = 6. Price isP∗market = 3Q∗ = 18. (Check that P = 60− 7(6) = 60− 42 = 18.)
2. With external costs
The true cost should be MC = 3Q + 4. Solve again. Note beforesolving that P∗
SC > P∗market , and Q∗
market > Q∗SC .
Set 3Q + 4 = 60− 7Q, or 10Q = 56, which implies that Q∗SC = 5.6.
To find price, P∗SC = 3Q∗ + 4 = 3(5.6) + 4 = 16.8 + 4 = 20.8.
Check that P∗SC = 60− 7(5.6) = 60− 39.2 = 20.8.