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Chapter 2
The Basics of
Supply and
Demand

Topics to Be Discussed


Supply and Demand



The Market Mechanism



Changes in Market Equilibrium



Elasticities of Supply and Demand



Short-Run Versus Long-Run Elasticities
Chapter 2: The Basics of Supply and

Slide 2

Topics to Be Discussed


Understanding and Predicting the Effects
of Changing Market Conditions



Effects of Government Intervention--Price
Controls

Chapter 2: The Basics of Supply and

Slide 3

Introduction


Applications of Supply and Demand
Analysis
Understanding

and predicting how world
economic conditions affect market price and
production

Analyzing

the impact of government price
controls, minimum wages, price supports,
and production incentives

Chapter 2: The Basics of Supply and

Slide 4

Introduction


Applications of Supply and Demand
Analysis
Analyzing

how taxes, subsidies, and import
restrictions affect consumers and producers

Chapter 2: The Basics of Supply and

Slide 5

Supply and Demand


The Supply Curve
The

supply curve shows how much of a good
producers are willing to sell at a given price,
holding constant other factors that might
affect quantity supplied

Chapter 2: The Basics of Supply and

Slide 6

Supply and Demand


The Supply Curve
This

price-quantity relationship can be shown
by the equation:

Qs  QS (P )

Chapter 2: The Basics of Supply and

Slide 7

Supply and Demand
The
TheSupply
Supply
Curve
CurveGraphically
Graphically

Price
($ per unit)
Vertical axis measures
price (P) received
per unit in dollars

Horizontal axis measures
quantity (Q) supplied in
number of units per
time period
Quantity

Chapter 2: The Basics of Supply and

Slide 8

Supply and Demand
Price
($ per unit)

S

The
TheSupply
Supply
Curve
CurveGraphically
Graphically

P2
The supply curve slopes
upward demonstrating that
at higher prices firms
will increase output

P1

Q1

Q2

Quantity

Chapter 2: The Basics of Supply and

Slide 9

Supply and Demand


Non-price Determining Variables of
Supply
Costs

of Production



Labor



Capital



Raw Materials

Chapter 2: The Basics of Supply and

Slide

Supply and Demand
Change
Changein
inSupply
Supply



The cost of raw
materials falls


At P1, produce Q2



At P2, produce Q1



Supply curve shifts right
to S’



P

S

S’

P1
P2

More produced at any
price on S’ than on S
Q0

Chapter 2: The Basics of Supply and

Q1

Q2

Slide

Q

Supply and Demand


Supply - A Review
Supply

is determined by non-price supplydetermining variables as such as the cost of
labor, capital, and raw materials.

Changes

in supply are shown by shifting the
entire supply curve.

Chapter 2: The Basics of Supply and

Slide

Supply and Demand


Supply - A Review
Changes

in quantity supplied are shown by
movements along the supply curve and are
caused by a change in the price of the
product.

Chapter 2: The Basics of Supply and

Slide

Supply and Demand


The Demand Curve
The

demand curve shows how much of a
good consumers are willing to buy as the
price per unit changes holding non-price
factors constant.

This

price-quantity relationship can be shown
by the equation:

QD  QD(P)
Chapter 2: The Basics of Supply and

Slide

Supply and Demand
Price
($ per unit)
Vertical axis measures
price (P) paid
per unit in dollars

Horizontal axis measures
quantity (Q) demanded in
number of units per
time period

Quantity

Chapter 2: The Basics of Supply and

Slide

Supply and Demand
Price
($ per unit)

The demand curve slopes
downward demonstrating
that consumers are willing
to buy more at a lower price
as the product becomes
relatively cheaper and the
consumer’s real income
increases.

D
Quantity

Chapter 2: The Basics of Supply and

Slide

Supply and Demand


Non-price Determining Variables of
Demand
Income
Consumer
Price

Tastes

of Related Goods



Substitutes



Complements

Chapter 2: The Basics of Supply and

Slide

Supply and Demand
Change
Changein
inDemand
Demand



Income Increases

P

D’

P2



At P1, produce Q2



At P2, produce Q1



Demand Curve shifts right P1



D

More purchased at any
price on D’ than on D

Q0

Chapter 2: The Basics of Supply and

Q1

Q2

Slide

Q

Shifts in Supply and Demand


Demand - A Review
Demand

is determined by non-price demanddetermining variables, such as, income, price
of related goods, and tastes.

Changes

in demand are shown by shifting
the entire demand curve.

Changes

in quantity demanded are shown by
movements along the demand curve.

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism
Price
($ per unit)

S
The curves intersect at
equilibrium, or marketclearing, price. At P0 the
quantity supplied is equal
to the quantity demanded
at Q0 .

P0

D
Q0

Quantity

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism


Characteristics of the equilibrium or
market clearing price:
QD

= QS

No

shortage

No

excess supply

No

pressure on the price to change

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism
Price
($ per unit)

S
Surplus

P1

If price is above equilibrium:
1) Price is above the
market clearing price
2) Qs > Qd
3) Price falls to the
market-clearing price

P0

D
Q0

Quantity

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism
A
ASurplus
Surplus


The market price is above equilibrium
 There

is excess supply

 Producers

lower prices

 Quantity

demanded increases and quantity
supplied decreases

 The

market continues to adjust until the
equilibrium price is reached.

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism
Price
($ per unit)

S

Surplus
P1

Assume the price is P1 , then:
1) Qs : Q1 > Qd : Q2
2) Excess supply is Q1:Q2.
3) Producers lower price.
4) Quantity supplied decreases
and quantity demanded
increases.
5) Equilibrium at P2Q3

P2

D
Q1

Q3

Q2 Quantity

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism
Surplus
Surplus -- Review:
Review:


The market price is above equilibrium:
There

is excess supply

Producers

lower prices

Quantity

demanded increases and quantity
supplied decreases

The

market continues to adjust until the
equilibrium price is reached

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism
Price
($ per unit)

S

P3

P2

Shortage
Q1

Q3

Assume the price is P2 , then:
1) Qd : Q2 > Qs : Q1
2) Shortage is Q1:Q2.
3) Producers raise price.
4) Quantity supplied increases
and quantity demanded
decreases.
5) Equilibrium at P3, Q3

D
Q2 Quantity

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism
Shortage
Shortage


The market price is below equilibrium:
There

is a shortage

Producers

raise prices

Quantity

demanded decreases and quantity
supplied increases

The

market continues to adjust until the new
equilibrium price is reached.

Chapter 2: The Basics of Supply and

Slide

The Market Mechanism


Market Mechanism Summary
1) Supply and demand interact to
determine the market-clearing price.
2) When not in equilibrium, the market
will
adjust to alleviate a shortage or
surplus and return the market to equilibrium.
3) Markets must be competitive for the
mechanism to be efficient.
Chapter 2: The Basics of Supply and

Slide

Changes In Market Equilibrium


Equilibrium prices are determined by the
relative level of supply and demand.



Supply and demand are determined by
particular values of supply and demand
determining variables.



Changes in any one or combination of these
variables can cause a change in the
equilibrium price and/or quantity.
Chapter 2: The Basics of Supply and

Slide

Changes In Market Equilibrium


Raw material prices
fall


P

D

S

S’

S shifts to S’

 Surplus

@ P1 of Q1,

Q2
 Equilibrium

P1
P3

@ P3, Q3

Q1 Q3 Q2

Chapter 2: The Basics of Supply and

Slide

Q

Changes In Market Equilibrium


Income Increases
 Demand
 Shortage

P

D

D’

S

shifts to D1
@ P1 of Q1, Q2 P3

 Equilibrium

@ P3 , Q 3

P1

Q2 Q1 Q3

Chapter 2: The Basics of Supply and

Slide

Q

Changes In Market Equilibrium


Income Increases &
raw material prices fall
increase in D is
greater than the
increase in S

P

D

D’

S

S’

 The

P2
P1

 Equilibrium

price and
quantity increase to P2,
Q2
Q1

Chapter 2: The Basics of Supply and

Q2

Slide

Q

Shifts in Supply and Demand


When supply and demand change
simultaneously, the impact on the
equilibrium price and quantity is
determined by:
1) The relative size and direction of the
change
2) The shape of the supply and demand
models
Chapter 2: The Basics of Supply and

Slide

The Price of Eggs and the Price
of a College Education Revisited


The real price of eggs fell 59% from 1970
to 1998.



Supply increased due to the increased
mechanization of poultry farming and the
reduced cost of production.



Demand decreased due to the increasing
consumer concern over the health and
cholesterol consequences of eating eggs.
Chapter 2: The Basics of Supply and

Slide

Market for Eggs
P

Prices fell until
a new equilibrium
was reached at $0.26
and a quantity
of 5,300 million dozen

S1970

(1970

dollars per
dozen)

S1998
$0.61

$0.26

D1970
5,300 5,500

D1998
Q (million dozens)

Chapter 2: The Basics of Supply and

Slide

The Price of a College Education


The real price of a college education rose
68 percent from 1970 to 1995.



Supply decreased due to higher costs of
equipping and maintaining modern
classrooms, laboratories and libraries, and
higher faculty salaries.



Demand increased due a larger
percentage of a larger number of high
school graduates attending college.
Chapter 2: The Basics of Supply and

Slide

Market for a College Education
P

S1995

(annual cost
in 1970
dollars)

$4,248

Prices rose until
a new equilibrium
was reached at $4,573
and a quantity
of 12.3 million students

S1970

$2,530

D1970
8.6

14.9

D1995

Q (millions of students enrolled))

Chapter 2: The Basics of Supply and

Slide

Changes In Market Equilibrium


Wage Inequality in the United States
Real

after-tax income from 1977 to 1999:



Rose 40+% for the top 20% of the income
distribution



Fell 10+% for the bottom 20%

Chapter 2: The Basics of Supply and

Slide

Consumption & Price of Copper
1880-1998

Chapter 2: The Basics of Supply and

Slide

The Long-Run Behavior
of Natural Resource Prices


Observations
Consumption

of copper has increased about
a hundred fold from 1880 through 1998
indicating a large increase in demand.

The

real price for copper has remained
relatively constant.

Chapter 2: The Basics of Supply and

Slide

Changes In Market Equilibrium
Price

S1900

S1950

S1998

Long-Run Path of
Price and Consumption

D1900

D1950

D1998

Quantity

Chapter 2: The Basics of Supply and

Slide

Changes In Market Equilibrium


Conclusion
Decreases

in the costs of production have
increased the supply by more than enough to
offset the increase in demand.

Chapter 2: The Basics of Supply and

Slide

Changes In Market Equilibrium


Observation
To accurately

predict the future price of a
product or service, it is necessary to consider
the potential change in supply and demand.

1970

predictions for oil and other minerals
proved incorrect because they only
considered the demand side of the market.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand


Generally, elasticity is a measure of the
sensitivity of one variable to another.



It tells us the percentage change in one
variable in response to a one percent
change in another variable.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Price
PriceElasticity
Elasticityof
ofDemand
Demand



Measures the sensitivity of quantity
demanded to price changes.
It

measures the percentage change in the
quantity demanded for a good or service that
results from a one percent change in the
price.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand



The price elasticity of demand is:

EP  (%Q)/(%P)

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Price
PriceElasticity
Elasticityof
ofDemand
Demand



The percentage change in a variable is
the absolute change in the variable
divided by the original level of the
variable.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Price
PriceElasticity
Elasticityof
ofDemand
Demand



So the price elasticity of demand is also:

Q/Q P Q
EP 

P/P Q P

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand


Interpreting Price Elasticity of Demand
Values
1) Because of the inverse relationship
between P and Q; EP is negative.
2) If EP > 1, the percent change in quantity is
greater than the percent change in
price.
We say the demand is price
elastic.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand


Interpreting Price Elasticity of Demand
Values
3) If EP < 1, the percent change in
quantity is less than the percent
change in price. We say the demand
is price inelastic.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Price
PriceElasticity
Elasticityof
ofDemand
Demand



The primary determinant of price
elasticity of demand is the availability of
substitutes.
Many
Few

substitutes demand is price elastic

substitutes demand is price inelastic

Chapter 2: The Basics of Supply and

Slide

Price Elasticities of Demand
Price
4

EP  - 
Q = 8 - 2P

The lower portion of
a downward sloping
demand curve is less elastic
than the upper portion.

Ep = -1
2

Linear Demand Curve
Q = a - bP
Q = 8 - 2P
Ep = 0
4

Chapter 2: The Basics of Supply and

8

Q

Slide

Price Elasticities of Demand
Price

Infinitely Elastic Demand

D

P*

EP  - 
Quantity

Chapter 2: The Basics of Supply and

Slide

Price Elasticities of Demand
Price

Completely Inelastic Demand

EP  0
Q*

Quantity

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Other
OtherDemand
DemandElasticities
Elasticities



Income elasticity of demand measures
the percentage change in quantity
demanded resulting from a one percent
change in income.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Other
OtherDemand
DemandElasticities
Elasticities



The income elasticity of demand is:

Q/Q
I Q
EI 

I/I
Q I
Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Other
OtherDemand
DemandElasticities
Elasticities



Cross elasticity of demand measures the
percentage change in the quantity
demanded of one good that results from
a one percent change in the price of
another good.



For example consider the substitute
goods, butter and margarine.
Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand


The cross elasticity of demand is:

Qb/Qb Pm Qb
EQbPm 

Pm/Pm Qb Pm


The cross elasticity for substitutes is positive,
while that for complements is negative.
Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Elasticities
Elasticitiesof
ofSupply
Supply



Price elasticity of supply measures the
percentage change in quantity supplied
resulting from a 1 percent change in price.



The elasticity is usually positive because
price and quantity supplied are directly
related.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
Elasticities
Elasticitiesof
ofSupply
Supply



We can refer to elasticity of supply with
respect to interest rates, wage rates, and the
cost of raw materials.

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
The
TheMarket
Marketfor
forWheat
Wheat



1981 Supply Curve for Wheat
QS



= 1,800 + 240P

1981 Demand Curve for Wheat
QD

= 3,550 - 266P

Chapter 2: The Basics of Supply and

Slide

Elasticities of Supply and Demand
The
TheMarket
Marketfor
forWheat
Wheat



Equilibrium: Q S = Q D

1,800  240 P  3,550  266 P
506 P  1,750
P  3.46 / bushel
Q  1,800  (240)(3.46)  2,630 million bushels
Chapter 2: The Basics of Supply and Demand

Slide 62

Elasticities of Supply and Demand
The
TheMarket
Marketfor
forWheat
Wheat

P QD
3.46
E 

(2.66)  .035 Inelastic
Q P
2,630
D
P

P QS
3.46
E 

(2.40)  .032 Inelastic
Q P 2,630
S
P

Chapter 2: The Basics of Supply and Demand

Slide 63

Elasticities of Supply and Demand
The
TheMarket
Marketfor
forWheat
Wheat



Assume the price of wheat is $4.00/bushel
QD  3,550  ( 266)(4.00)  2,486

4.00
Q 
( 266)  0.43
2,486
D
P

Chapter 2: The Basics of Supply and

Slide

Changes in the Market: 1981-1998
The
TheMarket
Marketfor
forWheat
Wheat

Supply (Qs) Demand (QD)

Equilibrium Price (Qs = QD)

1981

1800 + 240P

3550 - 266P

1800+240P = 3550-266P
506P = 1750
P1981 = $3.46/bushel

1998

1,944 + 207P

3,244 - 283P

1,944+207P = 3,244-283P
P1998 = $2.65/bushel

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

Demand
Demand


Price elasticity of demand varies with the
amount of time consumers have to
respond to a price.

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

Demand
Demand


Most goods and services:
Short-run

elasticity is less than long-run
elasticity. (e.g. gasoline, Drs.)



Other Goods (durables):
Short-run

elasticity is greater than long-run
elasticity (e.g. automobiles)

Chapter 2: The Basics of Supply and

Slide

Gasoline: Short-Run and
Long-Run Demand Curves
Price

DSR

People tend to
drive smaller and
more fuel efficient
cars in the long-run

Gasoline

DLR

Quantity

Chapter 2: The Basics of Supply and

Slide

Automobiles: Short-Run and
Long-Run Demand Curves
Price

DLR
People may put
off immediate
consumption, but
eventually older cars
must be replaced.

Automobiles

DSR

Quantity

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

Income
IncomeElasticities
Elasticities


Income elasticity also varies with the
amount of time consumers have to
respond to an income change.

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

Income
IncomeElasticities
Elasticities


Most goods and services:
Income

elasticity is greater in the long-run
than in the short run.


Higher incomes may be converted into
bigger cars so the income elasticity of
demand for gasoline increases with time.

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

Income
IncomeElasticities
Elasticities


Other Goods (durables):
Income

elasticity is less in the long-run than
in the short-run.


Originally, consumers will want to hold
more cars.



Later, purchases will only to be to replace
old cars.

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

The
TheDemand
Demandfor
for
Gasoline
Gasolineand
andAutomobiles
Automobiles



Gasoline and automobiles are
complementary goods.

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

The
TheDemand
Demandfor
for
Gasoline
Gasolineand
andAutomobiles
Automobiles



Gasoline
The

long-run price and income elasticities
are larger than the short-run elasticities.



Automobiles
The

long-run price and income elasticities
are smaller than the short-run elasticities.

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities
The
TheDemand
Demandfor
forGasoline
Gasoline

Years Following Price or Income Change
Elasticity

1

2

3

4

5

6

Price

-0.11 -0.22 -0.32 -0.49 -0.82 -1.17

Income

0.07 0.13

0.20

0.32

Chapter 2: The Basics of Supply and

0.54

0.78

Slide

Short-Run Versus
Long-Run Elasticities
The
TheDemand
Demandfor
forAutomobiles
Automobiles

Years Following Price or Income Change
Elasticity
Price
Income

1

2

3

4

5

6

-1.20 -0.93 -0.75 -0.55 -0.42 -0.40
3.00 2.33

1.88

1.38

Chapter 2: The Basics of Supply and

1.02

1.00

Slide

Short-Run Versus
Long-Run Elasticities

The
TheDemand
Demandfor
for
Gasoline
Gasolineand
andAutomobiles
Automobiles



Data Explains:
1) Why the price of oil did not continue to
rise above $30/barrel even though it
rose very rapidly in the early 1970s.
2) Why automobile sales are so sensitive
to the business cycle.
Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities
Supply
Supply


Most goods and services:
Long-run

price elasticity of supply is greater
than short-run price elasticity of supply.



Other Goods (durables, recyclables):
Long-run

price elasticity of supply is less
than short-run price elasticity of supply

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Primary
and
PrimaryCopper:
Copper:Short-Run
Short-Run
and
Long-Run
Elasticities
Long-Run
Long-RunSupply
SupplyCurves
Curves
Price

SSR
SLR
Due to limited
capacity, firms
are limited by
output constraints
in the short-run.
In the long-run, they
can expand.

Quantity

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Secondary
Copper:
and
Secondary
Copper:Short-Run
Short-Run
and
Long-Run
Elasticities
Long-Run
Long-RunSupply
SupplyCurves
Curves
Price

SLR

SSR

Price increases
provide an incentive
to convert scrap
copper into new supply.
In the long-run, this
stock of scrap copper
begins to fall.
Quantity

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

Supply
Supplyof
of Copper
Copper

Price Elasticity of:

Short-run

Long-run

Primary supply

0.20

1.60

Secondary supply

0.43

0.31

Total supply

0.25

1.50

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities

Weather
Weatherin
in Brazil
Brazil and
and
the
theprice
priceof
of Coffee
Coffee
in
inNew
New York
York


Elasticity explains why coffee prices are
very volatile.
Due

to the differences in supply elasticity in
the long-run and short run.

Chapter 2: The Basics of Supply and

Slide

Price of Brazilian Coffee

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities
Coffee
Coffee
S’ S
Price

A freeze or drought
decreases the supply
of coffee

P1

P0
Short-Run
1) Supply is completely inelastic
2) Demand is relatively inelastic
3) Very large change in price

D
Q1

Q0

Quantity

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities
Coffee
Coffee
Price

S’

S

P2
P0

Intermediate-Run
1) Supply and demand are
more elastic
2) Price falls back to P2.
3) Quantity falls to Q2

D
Q2 Q0

Quantity

Chapter 2: The Basics of Supply and

Slide

Short-Run Versus
Long-Run Elasticities
Coffee
Coffee
Price
Long-Run
1) Supply is extremely elastic.
2) Price falls back to P0.
3) Quantity increase to Q0.

S

P0

D
Q0

Quantity

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


First, we must learn how to “fit” linear
demand and supply curves to market
data.



Then we can determine numerically how
a change in a variable will cause supply
or demand to shift and thereby affect the
market price and quantity.

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Available Data
Equilibrium

Price, P*

Equilibrium

Quantity, Q*

Price

elasticity of supply, ES, and
demand, ED.

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions
Price

Supply: Q = c + dP

a/b

ED = -bP*/Q*
ES = dP*/Q*

P*

-c/d

Demand: Q = a - bP
Q*

Quantity

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Let’s begin with the equations for supply
and demand:
Demand: QD = a - bP
Supply:



QS = c + dP

We must choose numbers for a, b, c,
and d.
Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Step 1:
Recall:

E  (P/Q)( Q/P)

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


For linear demand curves, the change in
quantity divided by the change in price is
constant (equal to the slope of the curve).

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Substituting the slopes for each into the
formula for elasticity, we get:

ED  - b(P * /Q*)

ES  d(P * /Q*)
Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Since we will have values for ED, ES, P*,
and Q*, we can solve for b & d, and a &
c.

*

*

*

*

QD  a  bP
QS  c  dP

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Deriving the long-run supply and demand
for copper:
The

relevant data are:



Q* = 7.5 mmt/yr.



P* = 75 cents/pound



ES = 1.6



ED = -0.8

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Es = d(P*/Q*)



Ed = -b(P*/Q*)



1.6 = d(75/7.5)
= 0.1d



-0.8 = -b(.75/7.5)
= -0.1b



d = 1.6/0.1 = 16



b = 0.8/0.1 = 8

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Supply = QS* = c + dP*



Demand = QD* = a -bP*



7.5 = c + 16(0.75)



7.5 = a -(8)(.75)



7.5 = c + 12



7.5 = a - 6



c = 7.5 - 12



a = 7.5 + 6



c = -4.5



a =13.5



Q = -4.5 + 16P



Q = 13.5 - 8P

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Setting supply equal to demand gives:
Supply = -4.5 + 16p = 13.5 - 8p = Demand
16p + 8p = 13.5 + 4.5
p = 18/24 = .75

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions
Price

Supply: QS = -4.5 + 16P

a/b

.75

-c/d

Demand: QD = 13.5 - 8P
7.5

Mmt/yr

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


We have written supply and demand so
that they only depend upon price.



Demand could also depend upon income.



Demand would then be written as:

Q  a  bP  fI

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


We know the following information
regarding the copper industry:
I

= 1.0

P*

= 0.75

Q*

= 7.5

b

=8

Income

elasticity: E = 1.3

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


f can be found by substituting known
values into the income elasticity formula:

E  ( I / Q)(Q / I )
and

f  Q / I
Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Solving for f gives:
1.3 = (1.0/7.5)f
f = (1.3)(7.5)/1.0 = 9.75

Chapter 2: The Basics of Supply and

Slide

Understanding and Predicting the Effects
of Changing Market Conditions


Solving for a gives:

Q  a  bP  fI
*

*

7.5 = a - 8(0.75) + 9.75(1.0)
a = 3.75

Chapter 2: The Basics of Supply and

Slide

Declining Demand and the
Behavior of Copper Prices


The relevant factors leading to a
decrease in the demand for copper are:
1) A decrease in the growth rate of power
generation
2) The development of substitutes: fiber
optics and aluminum

Chapter 2: The Basics of Supply and

Slide

Real versus Nominal
Prices of Copper 1965 - 1999

Chapter 2: The Basics of Supply and

Slide

Real versus Nominal
Prices of Copper 1965 - 1999


We will try to estimate the impact of a 20
percent decrease in the demand for
copper.



Recall the equation for the demand
curve:
Q = 13.5 - 8P

Chapter 2: The Basics of Supply and

Slide

Real versus Nominal
Prices of Copper 1965 - 1999


Multiply this equation by 0.80 to get the
new equation. This gives:
Q = (0.80)(13.5 - 8P)
Q = 10.8 - 6.4P



Recall the equation for supply:
Q = -4.5 + 16P
Chapter 2: The Basics of Supply and

Slide

Real versus Nominal
Prices of Copper 1965 - 1999


The new equilibrium price is:
-4.5 + 16P = 10.8 - 6.4P
-16P + 6.4P = 10.8 + 4.5
P = 15.3/22.4
P = 68.3 cents/pound
Chapter 2: The Basics of Supply and

Slide

Real versus Nominal
Prices of Copper 1965 - 1999


The twenty percent decrease in demand
resulted in a reduction in the equilibrium
price to 68.3 cents from 75 cents, or 10
percent.

Chapter 2: The Basics of Supply and

Slide

Price of Crude Oil

Chapter 2: The Basics of Supply and

Slide

Upheaval in the World Oil Market


We can predict numerically the impact of
a decrease in the supply of OPEC oil.



In 1995:
P*

= $18/barrel

World

demand and total supply = 23 bb/yr.

OPEC

supply = 10 bb/yr.

Non-OPEC

supply = 13 bb/yr

Chapter 2: The Basics of Supply and

Slide

Price Elasticity Estimates
Short-Run Long-Run

World Demand:
Competitive Supply
(non-OPEC)

-0.05

-0.40

0.10

0.40

Chapter 2: The Basics of Supply and

Slide

Upheaval in the World Oil Market


Short-Run Impact of a stoppage of Saudi
Production equal to 3 bb/yr.
Short-run


D = 24.08 - 0.06P

Short-run


Demand
Competitive Supply

SC = 11.74 + 0.07P

Chapter 2: The Basics of Supply and

Slide

Upheaval in the World Oil Market


Short-Run Impact of a stoppage of Saudi
Production equal to 3 bb/yr.
Short-run

Total Supply--before supply
reduction (includes OPEC, 10bb/yr)


ST = 21.74 + 0.07P

Short-run


Total Supply--after supply reduction

ST = 18.74 + 0.07P

Chapter 2: The Basics of Supply and

Slide

Upheaval in the World Oil Market


New Price After Reduction
Demand = Supply
24.08 - 0.06P = 18.74 + 0.07P
P = 41.08

Chapter 2: The Basics of Supply and

Slide

Impact of Saudi Production Cut
SC

D S’T ST

Price 45
($ per
barrel) 40

Short-Run
Effect

35
30
25
20
18
15
10
5
0

5

10

15

20 23 25

Chapter 2: The Basics of Supply and

30

Quantity
35 (billions barrels/yr)

Slide

Upheaval in the World Oil Market


Long-Run Impact of a stoppage Saudi
Production equal to 3 bb/yr..
Long-run


D = 32.18 - 0.51P

Long-run


Demand
Total Supply

S = 17.78 + 0.29P

Chapter 2: The Basics of Supply and

Slide

Upheaval in the World Oil Market


New Price is found setting long-run
supply equal to long-run demand:
32.18 - 0.51P = 14.78 + 0.29P
P = 21.75

Chapter 2: The Basics of Supply and

Slide

Impact of Saudi Production Cut
Price 45

SC

D

($ per
barrel) 40

S’T ST

Long-run Effect
Due to the elasticity
of the long-run
supply and demand
curves, the long-run
effect of a cut
in production is
much less.

35
30
25
20
18
15
10
5
0

5

10

15

20 23 25

Chapter 2: The Basics of Supply and

30

35

Quantity
(billions barrels/yr)

Slide

Effects of Government Intervention
--Price Controls


If the government decides that the
equilibrium price is too high, they may
establish a maximum allowable ceiling
price.

Chapter 2: The Basics of Supply and

Slide

Effects of Price Controls
Price
S
If price is regulated to
be no higher than Pmax,
quantity supplied falls
to Q1 and quantity
demanded increases to
Q2. A shortage results

P0

Pmax

D
Excess demand

Q0

Chapter 2: The Basics of Supply and

Quantity

Slide

Price Controls and
Natural Gas Shortages


In 1954, the federal government began
regulating the wellhead price of natural
gas.



In 1962, the ceiling prices that were
imposed became binding and shortages
resulted.

Chapter 2: The Basics of Supply and

Slide

Price Controls and
Natural Gas Shortages


Price controls created an excess demand
of 7 trillion cubic feet.



Price regulation was a major component
of U.S. energy policy in the 1960s and
1970s, and it continued to influence the
natural gas markets in the 1980s.

Chapter 2: The Basics of Supply and

Slide

Price Controls and
Natural Gas Shortages

The
TheData:
Data: Natural
NaturalGas
Gas

PES  0.2
Cross elasticity of supply for oil  0.1
D
PE

 0.5

Cross elasticity of demand for oil  1.5
Supply : Q  14  2 PG  .25 PO
Demand : Q  5 PG  3.75 PO
Supply  Demand @ $2/TcF
Chapter 2: The Basics of Supply and

Slide

Price Controls and
Natural Gas Shortages

The
TheData:
Data: Natural
NaturalGas
Gas

1975 regulated price  $1.00
At $1.00/TcF
QS  18 TcF and Q  25 TcF
Shortage  7 TcF/yr
Chapter 2: The Basics of Supply and

Slide

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