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Market Failure
Diagrams
Learning Objective:To understand how to illustrate market failure with
diagrams
Learning Outcome / Success CriteriaDraw over/under productionDraw over/under consumption
This is the diagram that we use to show how the market works
Now assume that there is market failure and the market produces too much
There are negative externalities What curve do we need to add and
where?
Price
Quantity
D
S
Q*
P*
Q* = socially optimum quantityP* = socially optimum price
When it is firms that are producing too much we need to add another supply curve
Where do we need to add it to show too much production (more Q?)
More = Right – Add curve to the right (S1) Note that we do not talk about this being a shift
– this is just adding a curve to illustrate market failure
Now we talk about movement….. If there is too much production govt needs to
get S1 to shift inwards (left) and get closer to the socially optimum of Q*
How can we get supply curves to shift to the left?
Increase the firm’s costs
Price
Quantity
D
S
Q1
S1
Q*
Q* = socially optimum quantityP* = socially optimum price
So government needs to find a way to force supply to decrease
Or increase firm’s costs to reduce the overproduction
How could it do that? Introducing pollution permits
Price
Quantity
D
S
Q1
S1
Q*
Q* = socially optimum quantityP* = socially optimum price
Time for you to draw Draw an overproduction diagram on
your white boards
Back to our perfect market diagram This time we are going to change it so that there is market
failure and the market produces too little – positive externality
What curve do we need to add and where?
Price
Quantity
D
S
Q*
P*Q* = socially optimum quantityP* = socially optimum price
When it is firms that are producing too little it is the supply curve that needs to be added
To get closer to the socially optimum which way does the supply curve need to shift?
MoRe – Right What makes the curve shift to the right? A decrease in the firm’s costs
Price
Quantity
D
S
Q1
S1
Q*
So government needs to either make it produce more Or decrease it’s costs How could it do that? A subsidy
Price
Quantity
D
S
Q1
S1
Q*
Time for you to draw Draw an under-production diagram on
your white boards
Back again to our perfect market Now assume that there is market failure and the market
consumes too much This is a market for demerit goods Which curve needs to be added and
where?
Price
Quantity
D
S
Q*
P*
When we think of consumption we need to think of the demand curve
If the market is consuming too much we need to add a demand curve to show too much Q (Q1)
If government wants to reduce the market failure which way does it need to shift the demand curve?
We need to get less consumption less - left Price
Quantity
D1
S
Q1
D
Q*
Government needs to do something to shift demand What can it do? It could educate This would shift demand What else?
Price
Quantity
D1
S
Q1
D
Q*
It could also increase the price which would cause a contraction of demand.
How? It could place an indirect tax on the product This would shift the supply curve The price would increase Demand would contract to Q* Could government actually reduce it to Q*? Probably not because the tax would need to be so
high that it might put the cigarette companies out of business
It can still reduce the market failure
Price
Quantity
D
S
Q1
P1
S1
Q*
P*
Time for you to draw Draw an over-consumption diagram on
your white boards
Back again to our perfect market Now assume that there is market failure and the market
consumes too little This is a market for merit goods Which curve needs to be added
and where?
Price
Quantity
D
S
Q*
P*
If the market is consuming too little we need to add a demand curve
Where? There is not enough consumption so we need to add to the
left (we need to illustrate less Q)
Price
Quantity
D1
S
Q1
D
Q*
Government needs to do something to shift demand What can it do? It could educate This would shift demand Giving more Q (Q*) What else?
Price
Quantity
D1
S
Q1
D
Q*
It could also decrease the price which would cause an extension of demand.
How? It could subsidise the product/service This would shift the supply curve The price would decrease Demand would extend to Qso Could government subsidise enough to get
to Qso?
Price
Quantity
D
S1
Q*
P1S
Q1
P*
Time for you to draw Draw an under-consumption diagram
on your white boards
Time for you to draw Draw the following
Over-consumption Under consumption Over production Under production
Learning Objective:To understand how to illustrate market failure diagrams
with the proper notation
Learning Outcome / Success CriteriaDraw over/under production diagrams Successfully answer a 10 mark
question
When we draw market failure diagrams we change the labelling slightly
Often the price axis becomes costs and benefits (there is no penalty for leaving at Price)
The supply curve is the Marginal Social Cost curve (MSC) The demand curve is the Marginal Social Benefits curve (MSB)
Costs & Benefits
Quantity
MSB
MSC
Q*
P*
Marginal Social Cost (Remember we associate supply with costs)
Marginal Social Benefits (Remember we associate demand with benefits)
When the market is working properly we have allocative efficiency
The perfect market with the socially optimum output (Q*) The Marginal Social Costs equal the Marginal Social Benefits Consumer surplus and Producer Surplus are maximised
Too much production happens because the firms only think about their private costs (Marginal Private Costs)
They think about their profit They are profit maximisers They don’t think about the cost to third parties
(external costs) The marginal social costs are larger
than the marginal private costs
Costs & Benefits
Quantity
MSB
MSC
Q1
P1
MPC
Q*
P*
The external cost in this case is what? It is the pollution to those not involved in the
production The external cost is the vertical distance
between the MPC and MSC curve EC is the negative externality MPC + EC = MSC When MPC is not equal to MSB there is market
failure
Costs & Benefits
Quantity
MSB
MSC
Q1
P1
MPC
Q*
P*
EC
When MPC is not equal to MSC there is market failure
So Government can use the market to fix the failure
It can try to make MPC equal to MSC They increase the private costs
by making the firms pay for the pollution permits
Costs & Benefits
Quantity
MSB
MSC
Q1
P1
MPC
Q*
P*
EC
When there are negative externalities there is welfare loss We can illustrate this using this diagram The turquoise triangle shows the size of the welfare loss
Remember that when you draw the welfare loss for a negative externality it points towards the zero (think of a number line – the negative numbers are behind the zero – the triangle points towards the negative numbers!!
By taxing the firm The marginal private costs increase The supply decreases The quantity reduces from Q1 to Q2 The welfare loss is decreased The turquoise triangle is decreased The quantity is closer to Q*
The socially optimum amount is Q* but to get this amount government would have to accurately measure the external cost (the pollution) and also the tax may be so large that firms may exit the market
Q2 is still better than Q1
Time for you to draw Draw a negative externality diagram on
your white boards
This diagram illustrates a positive externality The socially optimum amount is Q* Firms in this market are not producing
enough This time they are only thinking about
their benefits and not the benefits to society
There is potential welfare gain if more is produced (turquoise triangle)
Remember that when you draw the welfare loss for a positive externality it points away from zero (think of a number line – the positive numbers are in front of the zero – the triangle points towards the positive numbers!!
Time for you to draw Draw a positive externality diagram on
your white boards
Learning Objective:To understand how to illustrate over and under
consumption market failure with diagrams
Learning Outcome / Success CriteriaDraw over/under consumption Successfully answer a 10 mark
question
This diagram illustrates a negative externality in consumption
Too much consumption of a demerit good Consumers are only thinking about their
costs and benefits There is welfare loss that needs to
be reduced
Again the triangle is pointing to the negative!
With either of these solutions the triangle will reduce
The socially optimum amount is Q* but to get this amount government would have to accurately measure the external costs/benefits. To reduce the triangle (rather than remove it) and have a quantity less than Q1 will be an improvement
Time for you to draw Draw a positive externality diagram on
your white boards
This diagram illustrates a positive externality in consumption
Too little consumption of a merit good Consumers are only thinking about their
costs and benefits There is potential welfare gain
Again the triangle is pointing to the negative!
Positive externality points to the positive!
With either of these solutions the triangle reduces
The socially optimum amount is Q* but to get this amount government may have to pay large subsidies (opportunity cost). To reduce the triangle (rather than remove it) and have a quantity more than Q1 will be an improvement
Learning Objective:To understand how to illustrate market failure with
diagrams Learning Outcome / Success Criteria
Draw over/under productionDraw over/under consumption
Did we achieve these?