2. The Deadweight Loss of Taxation
• Tax on a good
– Levied on buyers
• Demand curve shifts downward by the size of tax
– Levied on sellers
• Supply curve shifts upward by the size of tax
– Same outcome: price wedge
• Price paid by buyers – rises
• Price received by sellers – falls
• Lower quantity sold
2
3. The Deadweight Loss of Taxation
• Tax burden
– Distributed between producers and
consumers
– Determined by elasticities of supply and
demand
• Market for the good - smaller
3
4. Figure
The effects of a tax
1
4
Price
Quantity
0
Demand
Supply
Price buyers pay
Price without tax
Price sellers receive
Size
of tax
A tax on a good places a wedge between the price that buyers pay and the price that
sellers receive. The quantity of the good sold falls.
Quantity
with tax
Quantity
without tax
5. The Deadweight Loss of Taxation
• How a tax affects market participants
• Gains and losses from a tax on a good
– Buyers: consumer surplus
– Sellers: producer surplus
– Government: total tax revenue
• Tax times quantity sold
• Public benefit from the tax
5
6. Figure
Tax revenue
2
6
Price
Quantity
0
Demand
Supply
The tax revenue that the government collects equals T × Q, the size of the tax T times
the quantity sold Q. Thus, tax revenue equals the area of the rectangle between the
supply and demand curves
Quantity
with tax
Quantity
without tax
Size of tax (T)
Quantity
sold (Q)
Tax
revenue
T Q
ˣ
Price buyers pay
Price sellers receive
7. The Deadweight Loss of Taxation
• Welfare without a tax
– Consumer surplus
– Producer surplus
– Total tax revenue = 0
• Welfare with tax
– Smaller consumer surplus
– Smaller producer surplus
– Total tax revenue
– Smaller overall welfare
7
8. Figure
How a tax affects welfare
3
8
Price
Quantity
0
Demand
Supply A tax on a good reduces
consumer surplus (by the area
B + C) and producer surplus
(by the area D + E). Because
the fall in producer and
consumer surplus exceeds tax
revenue (area B + D), the tax
is said to impose a
deadweight loss (area C + E).
A
B
D
F
Q1
C
E
Price
sellers
receive
=PS
Price
without
tax
=P1
Price
buyers
pay =PB
Q2
Without Tax With Tax Change
Consumer Surplus
Producer Surplus
Tax Revenue
Total Surplus
A+B+C
D+E+F
None
A+B+C+D+E+F
A
F
B+D
A+B+D+F
-(B+C)
-(D+E)
+(B+D)
-(C+E)
The area C + E shows
the fall in total surplus
and is the deadweight
loss of the tax
9. The Deadweight Loss of Taxation
• Losses of surplus to buyers and sellers from a
tax
– Exceed the revenue raised by the government
• Deadweight loss
– Fall in total surplus that results from a market
distortion, such as a tax
• Taxes distort incentives
– Markets allocate resources inefficiently
9
10. The Deadweight Loss of Taxation
• Deadweight losses and the gains from trade
– Taxes cause deadweight losses
• Prevent buyers and sellers from realizing some of
the gains from trade
– The gains from trade
• Difference between buyers’ value and sellers’ cost
• Less than the tax
• Once the tax is imposed
– Trades are not made
– Deadweight loss
10
11. Figure
The deadweight loss
4
11
Price
Quantity
0
Demand
Supply
When the government imposes a tax on a good, the quantity sold falls from Q1 to Q2. At every
quantity between Q1 and Q2, the potential gains from trade among buyers and sellers are not
realized. These lost gains from trade create the deadweight loss.
Q1
PS
Price
without tax
PB
Q2
Size
of tax
Value to
buyers
Cost to
sellers
Lost gains
from trade
Reduction in quantity due
to the tax
12. Determinants of the Deadweight Loss
• Price elasticities of supply and demand
– Supply curve - more elastic
• Deadweight loss – larger
– Demand curve – more elastic
• Deadweight loss – larger
• The greater the elasticities of supply and
demand
– The greater the deadweight loss of a tax
12
13. Figure
Tax distortions and elasticities (a, b)
5
13
Price
Quantity
0
(a) Inelastic supply
In panels (a) and (b), the demand curve and the size of the tax are the same, but the price
elasticity of supply is different. Notice that the more elastic the supply curve, the larger the
deadweight loss of the tax.
(b) Elastic supply
Size
of tax
When supply is
relatively inelastic,
the deadweight loss
of a tax is small
Price
Quantity
0
Size
of tax
When supply is
relatively elastic,
the deadweight loss
of a tax is large
Demand
Supply
Demand
Supply
14. Figure
Tax distortions and elasticities (c, d)
5
14
Price
Quantity
0
(c) Inelastic demand
In panels (c) and (d), the supply curve and the size of the tax are the same, but the price
elasticity of demand is different. Notice that the more elastic the demand curve, the larger the
deadweight loss of the tax.
(d) Elastic demand
Size
of tax
Demand
Supply
When demand is relatively
inelastic, the deadweight
loss of a tax is small
Price
Quantity
0
Size
of tax
Demand
Supply
When demand is relatively
elastic, the deadweight
loss of a tax is large
15. • How big should the government be?
– The larger the deadweight loss of taxation
• The larger the cost of any government program
– If taxes - large deadweight losses
• These losses - strong argument for a leaner government
– Does less and taxes less
– If taxes - small deadweight losses
• Government programs - less costly
The deadweight loss debate
15
16. • How big are the deadweight losses of taxation?
– Economists disagree
– Tax on labor
• Social Security tax, Medicare tax, federal income tax
• Places a wedge between the wage that firms pay and the
wage that workers receive
• Marginal tax rate on labor income = 40%
The deadweight loss debate
16
17. • 40% labor tax - Small or large deadweight loss?
– Labor supply - fairly inelastic
• Almost vertical
• Tax on labor - small deadweight loss
– Labor supply - more elastic
• Tax on labor – greater deadweight loss
The deadweight loss debate
17
18. Deadweight Loss & Tax Revenue as Taxes Vary
• As the tax increases
– Deadweight loss increases
• Even more rapidly than the size of the tax
– Tax revenue
• Increases initially
• Then decreases
– Higher tax – drastically reduces the size of the market
18
19. Figure
How deadweight loss and tax revenue vary with the
size of a tax (a, b, c)
6
19
Price
Quantity
0
(a) Small tax
The deadweight loss is the reduction in total surplus due to the tax. Tax revenue is the amount
of the tax times the amount of the good sold. In panel (a), a small tax has a small deadweight
loss and raises a small amount of revenue. In panel (b), a somewhat larger tax has a larger
deadweight loss and raises a larger amount of revenue. In panel (c), a very large tax has a
very large deadweight loss, but because it has reduced the size of the market so much, the
tax raises only a small amount of revenue.
Demand
Supply
Deadweight
loss
Q1
PB
PS
Q2
Tax
revenue
Price
Quantity
0
(b) Medium tax
Demand
Supply
Deadweight
loss
Q1
PB
PS
Q2
Tax
revenue
Price
Quantity
0
(c) Large tax
Demand
Supply
Deadweight
loss
Q1
PB
PS
Q2
Tax
revenue
20. Figure
How deadweight loss and tax revenue vary with the
size of a tax (d, e)
6
20
Deadweight
loss
Tax size
0
(d) From panel (a) to panel (c),
deadweight loss continually increases
Panels (d) and (e) summarize these conclusions. Panel (d) shows that as the size of a tax
grows larger, the deadweight loss grows larger. Panel (e) shows that tax revenue first rises
and then falls. This relationship is sometimes called the Laffer curve.
(e) From panel (a) to panel (c), tax
revenue first increases, then decreases
Tax
Revenue
Tax size
0
Laffer curve
21. • 1974, economist Arthur Laffer
– Laffer curve
– Supply-side economics
– Tax rates were so high
• Reducing them would actually raise tax revenue
• Ronald Reagan - ran for president in 1980
– From experience in film industry
• High tax rates - caused less work
• Low tax rates - caused more work
The Laffer curve and supply-side
economics
21
22. • Ronald Reagan - ran for president in 1980
– Argument
• Taxes were so high that they were discouraging hard work
• Lower taxes would give people the proper incentive to work
– Raise economic well-being
– Perhaps increase tax revenue
• Economists continue to debate Laffer’s argument
• General lesson:
– Change in tax revenue from a tax change
– Depends on how the tax change affects people’s behavior
The Laffer curve and supply-side
economics
22
