Economics Chapter 4 PowerPoint Slides

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Chapter 4
Demand, Supply, and
Market Equilibrium
In recent years, thousands of workers have
moved to North Dakota to work in the oil
industry. Between 2009 and 2012, mining
employment in the state increased by about
11,000 jobs and total employment increased
by over 40,000 jobs. Given the limited
options for increasing the housing stock in
the short run, the increase in the demand
for housing increased housing prices
dramatically. In the town of Williston, the
rent for a two-bedroom apartment increased
from $350 per month to $2,000.
Prepared By Brock Williams
Learning Objectives
1. Describe and explain the law of demand
2. Describe and explain the law of supply
3. Explain the role of price in reaching a market
equilibrium
4. Describe the effect of a change in demand on the
equilibrium price
5. Describe the effect of a change in supply on the
equilibrium price
6. Use information on price and quantity to
determine what caused a change in price
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4-2
DEMAND, SUPPLY, AND MARKET
EQUILIBRIUM
●perfectly competitive market
A market with many buyers and sellers of a
homogeneous product and no barriers to entry.
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4.1 THE DEMAND CURVE
●quantity demanded
The amount of a product that consumers are willing
and able to buy.
●demand schedule
A table that shows the relationship between the price of
a product and the quantity demanded, ceteris paribus.
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4-4
4.1 THE DEMAND CURVE (cont.)
Here is a list of the variables that affect an individual consumer’s
decision, using the pizza market as an example:
• The price of the product (for example, the price of a pizza)
• The consumer’s income
• The price of substitute goods (for example, the prices of tacos or
sandwiches or other goods that can be consumed instead of pizza)
• The price of complementary goods (for example, the price of
lemonade or other goods consumed with pizza)
• The consumer’s preferences or tastes and advertising that may
influence preferences
• The consumer’s expectations about future prices
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4.1 THE DEMAND CURVE (cont.)
The Individual Demand Curve and the Law of Demand
●individual demand curve
A curve that shows the relationship between the price of a
good and quantity demanded by an individual consumer,
ceteris paribus.
●law of demand
There is a negative relationship between price and
quantity demanded, ceteris paribus.
●change in quantity demanded
A change in the quantity consumers are willing and
able to buy when the price changes; represented
graphically by movement along the demand curve.
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4.1 THE DEMAND CURVE (cont.)
The Individual Demand
Curve and the Law of
Demand
 FIGURE 4.1
The Individual Demand Curve
According to the law of demand, the
higher the price, the smaller the
quantity demanded, everything else
being equal. Therefore, the demand
curve is negatively sloped: When
the price increases from $6 to $8,
the quantity demanded decreases
from seven pizzas per month (point
c) to four pizzas per month (point b).
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4-7
4.1 THE DEMAND CURVE (cont.)
From Individual Demand to Market Demand
 FIGURE 4.2
From Individual to Market
Demand
The market demand equals the
sum of the demands of all
consumers. In this case, there are
only two, so at each price the
market quantity demanded equals
the quantity demanded by Al plus
the quantity demanded by Bea.
At a price of $8, Al’s quantity is
four pizzas (point a) and Bea’s
quantity is two pizzas (point b), so
the market quantity demanded is
six pizzas (point c).
Each consumer obeys the law of
demand, so the market demand
curve is negatively sloped.
●market demand curve
A curve showing the relationship between price and quantity
demanded by all consumers, ceteris paribus.
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4-8
APPLICATION
1
LAW OF DEMAND AND CIGARETTES
APPLYING THE CONCEPTS #1: What is the Law of Demand?
• As price decreases and we move downward along the market demand for
cigarettes, the quantity of cigarettes demanded increases for two reasons.
First, people who smoked cigarettes at the original price respond to the
lower price by smoking more. Second, some people start smoking.
• A change in cigarette taxes in Canada illustrates the second effect, the
new-smoker effect. In 1994, several provinces in eastern Canada cut their
cigarette taxes and the price of cigarettes in the provinces decreased by
roughly 50 percent. Researchers tracked the choices of 591 youths from
the Waterloo Smoking Prevention Program, and concluded that the lower
price increased the smoking rate by roughly 17 percent.
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4-9
4.2 THE SUPPLY CURVE
Suppose you ask the manager of a firm, “How much of your product
are you willing to produce and sell?” The manager’s decision about
how much to produce depends on many variables, including the
following, using pizza as an example:
• The price of the product (for example, the price per pizza)
• The wage paid to workers
• The price of materials (for example, the price of dough and
cheese)
• The cost of capital (for example, the cost of a pizza oven)
• The state of production technology (for example, the knowledge
used in making pizza)
• Producers’ expectations about future prices
• Taxes paid to the government or subsidies (payments from the
government to firms to produce a product)
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4-10
4.2 THE SUPPLY CURVE (cont.)
The Individual Supply Curve and the Law of Supply
●quantity supplied
The amount of a product that firms are willing and
able to sell.
●supply schedule
A table that shows the relationship between the price
of a product and quantity supplied, ceteris paribus.
●individual supply curve
A curve showing the relationship between price and
quantity supplied by a single firm, ceteris paribus.
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4-11
4.2 THE SUPPLY CURVE (cont.)
The Individual Supply Curve and the Law of Supply
 FIGURE 4.3
The Individual Supply Curve
The supply curve of an individual
supplier is positively sloped,
reflecting the law of supply.
As shown by point a, the quantity
supplied is zero at a price of $2,
indicating that the minimum
supply price is just above $2.
An increase in price increases the
quantity supplied to 100 pizzas at
a price of $4, to 200 pizzas at a
price of $6, and so on.
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4-12
4.2 THE SUPPLY CURVE (cont.)
The Individual Supply Curve and the Law of Supply
●law of supply
There is a positive relationship between
price and quantity supplied, ceteris
paribus.
●change in quantity supplied
A change in the quantity firms are willing
and able to sell when the price changes;
represented graphically by movement
along the supply curve.
●minimum supply price
The lowest price at which a product will
be supplied.
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4-13
4.2 THE SUPPLY CURVE (cont.)
Why Is the Individual Supply Curve Positively Sloped?
MARGINAL PRINCIPLE
Consistent with the Law of Supply, increase the level of an activity as long as
its marginal benefit exceeds its marginal cost. Choose the level at which the
marginal benefit equals the marginal cost.
From Individual Supply to Market Supply
●market supply curve
A curve showing the relationship
between the market price and quantity
supplied by all firms, ceteris paribus.
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4.2 THE SUPPLY CURVE (cont.)
From Individual Supply to Market Supply
 FIGURE 4.4
From Individual to Market Supply
The market supply is the sum
of the supplies of all firms. In
Panel A, Lola is a low-cost
producer who produces the first
pizza once the price rises
above $2 (shown by point a).
Panel B, Hiram is a high-cost
producer who doesn’t produce
pizza until the price rises above
$6 (shown by point f ).
To draw the market supply
curve, we sum the individual
supply curves horizontally. At a
price of $8, market supply is
400 pizzas (point m), equal to
300 from Lola (point d) plus
100 from Hiram (point g).
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4.2 THE SUPPLY CURVE (cont.)
From Individual Supply to Market Supply
 FIGURE 4.5
The Market Supply
Curve with Many Firms
The market supply is the sum
of the supplies of all firms.
The minimum supply price is
$2 (point a), and the quantity
supplied increases by 10,000
for each $2 increase in price
to 10,000 at a price of $4
(point b), to 20,000 at a price
of $6 (point c), and so on.
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4-16
4.2 THE SUPPLY CURVE (cont.)
Why Is the Market Supply Curve Positively Sloped?
To explain the positive slope, consider the two responses by firms to an
increase in price:
• Individual firm. As we saw earlier, a higher price encourages a firm to
increase its output by purchasing more materials and hiring more
workers.
• New firms. In the long run, new firms can enter the market and
existing firms can expand their production facilities to produce more
output.
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4-17
APPLICATION
2
LAW OF SUPPLY AND WOOLYMPICS
APPLYING THE CONCEPTS #2: What is the Law of Supply?
• In the 1990s, the world price of wool decreased by about 30 percent, and prices
have remained relatively low since then. Based on the law of supply, we would
expect the quantity of wool supplied in New Zealand and other exporters to
decrease, and that’s what happened. Land that formerly grew grass for woolproducing sheep has been converted into other uses, including dairy products,
forestry, and the domestication of deer.
• There have been several attempts to revive the wool industry by boosting the
demand for wool and thus increase its price. The United Nations General
Assembly declared 2009 as the International Year of Natural Fibers, with the
objective “to raise awareness and stimulate demand for natural fibers.” In 2012,
the Federated Farmers of New Zealand proposed that sheep shearing be added
to the Commonwealth Games and Olympics as a demonstration sport. Of
course, it’s not obvious that Olympic shearing would increase the demand for
wool, and then there is the problem of what to do with all the sheared wool.
Extreme knitting?
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4-18
4.3 MARKET EQUILIBRIUM: BRINGING
DEMAND AND SUPPLY TOGETHER
●market equilibrium
A situation in which the quantity
demanded equals the quantity supplied
at the prevailing market price.
Excess Demand Causes the Price to Rise
●excess demand (shortage)
A situation in which, at the prevailing
price, the quantity demanded exceeds
the quantity supplied.
Excess Supply Causes the Price to Drop
●excess supply (surplus)
A situation in which the quantity supplied
exceeds the quantity demanded at the
prevailing price.
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4-19
4.3 MARKET EQUILIBRIUM: BRINGING
DEMAND AND SUPPLY TOGETHER (cont.)
 FIGURE 4.6
Market Equilibrium
At the market equilibrium (point
a, with price = $8 and quantity =
30,000), the quantity supplied
equals the quantity demanded.
At a price below the equilibrium
price ($6), there is excess
demand—the quantity
demanded at point c exceeds
the quantity supplied at point b.
At a price above the equilibrium
price ($12), there is excess
supply—the quantity supplied at
point e exceeds the quantity
demanded at point d.
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4-20
APPLICATION
3
SHRINKING WINE LAKES
APPLYING THE CONCEPTS #3: What are the consequences of a price
above the equilibrium price?
• Under the Common Agricultural Policy (CAP) the European Union uses a
number of policies to support the agricultural sectors of its member countries.
• Under a minimum-price policy the government sets a price above the marketequilibrium price. The EU guarantees farmers minimum prices for products
such as grain, dairy products, and wine. This policy causes artificial excess
supply: if the minimum price exceeds the market-equilibrium price, the quantity
supplied will exceed the quantity demanded.
• To support the minimum prices, the EU purchases any output that a farmer
cannot sell at the guaranteed price and stores the excess supply in facilities
labeled by the European press as “butter mountains” and “wine lakes.”
• In recent years the EU has reformed its agriculture policy by reducing and in
some cases eliminating minimum prices. As a result, the butter mountains and
wine lakes are shrinking.
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4-21
4.4 MARKET EFFECTS OF CHANGES IN
DEMAND
Change in Quantity Demanded versus Change in Demand
▼ FIGURE 4.7
Change in Quantity Demanded versus Change in Demand
(A) A change in price
causes a change in
quantity demanded, a
movement along a single
demand curve. For
example, a decrease in
price causes a move from
point a to point b,
increasing the quantity
demanded.
(B) A change in demand
caused by changes in a
variable other than the
price of the good shifts the
entire demand curve. For
example, an increase in
demand shifts the demand
curve from D1 to D2.
●change in demand
A shift of the demand curve caused by a change in
a variable other than the price of the product.
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4-22
4.4 MARKET EFFECTS OF CHANGES IN
DEMAND (cont.)
Increases in Demand Shift the Demand Curve
●normal good
A good for which an increase in income
increases demand.
●inferior good
A good for which an increase in income
decreases demand.
●substitutes
Two goods for which an increase in the price
of one good increases the demand for the
other good.
●complements
Two goods for which a decrease in the price
of one good increases the demand for the
other good.
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4-23
4.4 MARKET EFFECTS OF CHANGES IN
DEMAND (cont.)
Increases in Demand Shift the Demand Curve
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4-24
4.4 MARKET EFFECTS OF CHANGES IN
DEMAND (cont.)
Increases in Demand Shift the Demand Curve
 FIGURE 4.8
An Increase in Demand
Increases the Equilibrium Price
An increase in demand shifts the
demand curve to the right: At each
price, the quantity demanded
increases.
At the initial price ($8), there is excess
demand, with the quantity demanded
(point b) exceeding the quantity
supplied (point a).
The excess demand causes the price
to rise, and equilibrium is restored at
point c.
To summarize, the increase in
demand increases the equilibrium
price to $10 and increases the
equilibrium quantity to 40,000 pizzas.
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4-25
4.4 MARKET EFFECTS OF CHANGES IN
DEMAND (cont.)
Decreases in Demand Shift the Demand Curve
 FIGURE 4.9
A Decrease in Demand Decreases the
Equilibrium Price
A decrease in demand shifts the
demand curve to the left: At each
price, the quantity demanded
decreases.
At the initial price ($8), there is excess
supply, with the quantity supplied
(point a) exceeding the quantity
demanded (point b).
The excess supply causes the price to
drop, and equilibrium is restored at
point c.
To summarize, the decrease in
demand decreases the equilibrium
price to $6 and decreases the
equilibrium quantity to 20,000 pizzas.
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4-26
4.4 MARKET EFFECTS OF CHANGES IN
DEMAND (cont.)
Decreases in Demand Shift the Demand Curve
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4-27
APPLICATION
4
CHINESE DEMAND AND PECAN PRICES
APPLYING THE CONCEPTS #4: How does a change in demand
affect the equilibrium price?
• Between 2006 and 2009, Chinese imports of US pecans increased from 9
million pounds per year to 88 million pounds.
• The increase in demand from China is roughly 30 percent of the total
annual crop. The increase in demand was caused in part by widespread
reports in the Chinese media that pecans promote brain and
cardiovascular health.
• As a result of the increase in demand, the equilibrium price of pecans
increased by about 50 percent, increasing the price of pecan pie, a holiday
favorite.
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4-28
4.5 MARKET EFFECTS OF CHANGES IN
SUPPLY
Change in Quantity Supplied versus Change in Supply
 FIGURE 4.10
Change in Quantity Supplied versus Change in Supply
(A) A change in price causes a change in quantity supplied, a movement along a single supply curve.
For example, an increase in price causes a move from point a to point b.
(B) A change in supply (caused by a change in something other than the price of the product) shifts the
entire supply curve. For example, an increase in supply shifts the supply curve from S1 to S2. For any
given price (for example, $6), a larger quantity is supplied (25,000 pizzas at point c instead of 20,000 at
point a). The price required to generate any given quantity decreases. For example, the price required
to generate 20,000 pizzas drops from $6 (point a) to $5 (point d ).
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4-29
4.5 MARKET EFFECTS OF CHANGES IN
SUPPLY (cont.)
Increases in Supply Shift the Supply Curve
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4-30
4.5 MARKET EFFECTS OF CHANGES IN
SUPPLY (cont.)
An Increase in Supply Decreases the Equilibrium Price
 FIGURE 4.11
An Increase in Supply Decreases
the Equilibrium Price
An increase in supply shifts the
supply curve to the right: At each
price, the quantity supplied
increases.
At the initial price ($8), there is
excess supply, with the quantity
supplied (point b) exceeding the
quantity demanded (point a). The
excess supply causes the price to
drop, and equilibrium is restored
at point c.
To summarize, the increase in
supply decreases the equilibrium
price to $6 and increases the
equilibrium quantity to 36,000
pizzas.
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4-31
4.5 MARKET EFFECTS OF CHANGES IN
SUPPLY (cont.)
Decreases in Supply Shift the Supply Curve
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4-32
4.5 MARKET EFFECTS OF CHANGES IN
SUPPLY (cont.)
A Decrease in Supply Increases the Equilibrium Price
 FIGURE 4.12
A Decrease in Supply Increases
the Equilibrium Price
A decrease in supply shifts the supply
curve to the left. At each price, the
quantity supplied decreases.
At the initial price ($8), there is excess
demand, with the quantity demanded
(point a) exceeding the quantity
supplied (point b). The excess demand
causes the price to rise, and
equilibrium is restored at point c.
To summarize, the decrease in supply
increases the equilibrium price to $8
and decreases the equilibrium quantity
to 24,000 pizzas.
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4-33
4.5 MARKET EFFECTS OF CHANGES IN
SUPPLY (cont.)
Simultaneous Changes in Demand and Supply
 FIGURE 4.13
Market Effects of Simultaneous Changes in Demand and Supply
(A) Larger increase in demand. If the increase in demand is larger than the increase in supply (if the shift
of the demand curve is larger than the shift of the supply curve), both the equilibrium price and the
equilibrium quantity will increase.
(B) Larger increase in supply. If the increase in supply is larger than the increase in demand (if the shift of
the supply curve is larger than the shift of the demand curve), the equilibrium price will decrease and the
equilibrium quantity will increase.
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4-34
APPLICATION
5
HONEY BEES AND THE PRICE OF ICE CREAM
APPLYING THE CONCEPTS #5: How does a change in supply
affect the equilibrium price?
• In the last few years thousands of honeybee
colonies have vanished, a result of bee colony
collapse disorder (CCD). Roughly one-third of the
U.S. food supply—including a wide variety of fruits,
vegetables, and nuts—depends on pollination from
bees. The decline of honeybees threatens $15
billion worth of crops in the United States. The
decrease in pollination by bees has decreased the
supply of strawberries, raspberries, and almonds,
leading to higher prices for these ingredients for
ice cream. The higher prices for berries and nuts
have increased the cost of producing food
products, such as ice cream, increasing their
prices as well.
• The collapsing of bee colonies is a mystery. The
ice cream maker Hagen-Dazs donated money to
Pennsylvania State University and the University
of California, Davis to support research exploring
the causes of CCD and possible solutions.
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4-35
4.6 PREDICTING AND EXPLAINING
MARKET CHANGES
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4-36
APPLICATION
6
WHY LOWER DRUG PRICES?
APPLYING THE CONCEPTS #6: What explains a decrease in price?
• Ted Koppel, host of the ABC news program Nightline, once said, "Do you know
what's happened to the price of drugs in the United States? The price of cocaine,
way down, the price of marijuana, way down. You don't have to be an expert in
economics to know that when the price goes down, it means more stuff is coming
in. That's supply and demand." According to Koppel, the price of drugs dropped
because the government's efforts to control the supply of illegal drugs had failed. In
other words, the lower price resulted from an increase in supply.
• Is Koppel's economic detective work sound? In Table4.5, Koppel’s explanation of
lower prices is the third case--Increase in supply. This is the correct explanation
only if along with a decrease we experience an increase in the equilibrium quantity.
But according to the U.S. Department of Justice, the quantity of drugs consumed
actually decreased during the period of dropping prices. Therefore, the correct
explanation of lower prices is the second case--Decrease in demand. Lower
demand—not a failure of the government's drug policy and an increase in supply—
was responsible for the decrease in drug prices.
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4-37
4.7 APPLICATIONS OF DEMAND AND
SUPPLY
• We can apply what we’ve learned about demand and supply to real
markets.
• We can use the model of demand and supply to predict the effects of
various events on equilibrium prices and quantities.
• We can also explain some observed changes in equilibrium prices
and quantities.
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4-38
KEY
TERMS
change in demand
law of demand
change in quantity demanded
law of supply
change in quantity supplied
market demand curve
change in supply
market equilibrium
complements
market supply curve
demand schedule
minimum supply price
excess demand (shortage)
normal good
excess supply (surplus)
perfectly competitive market
individual demand curve
quantity demanded
individual supply curve
quantity supplied
inferior good
substitutes
supply schedule
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4-39
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