Unit 2:Demand, Supply, and

Consumer Choice

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DEMAND DEFINEDWhat is Demand?

Demand is the different quantities of goods that consumers are willing and able to buy at different prices.(Ex: vacant golf course lot in Sun Valley)

What is the Law of Demand? There is an INVERSE relationship between

price and quantity demanded

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Example of DemandI am willing to sell several A’s in AP Economics. How much will you pay?

Price Quantity

Demanded

Demand Schedule

3Copyright ACDC Leadership 2015

Why does the Law of Demand occur?

The law of demand is the result of three separate behavior patterns that overlap:

1.The Substitution effect

2.The Income effect

3.The Law of Diminishing Marginal Utility

We will define and explain each…4

• If the price goes up for a product, consumer buy less of that product and more of another substitute product (and vice versa) – Investopedia video clip

1. The Substitution Effect

Why does the Law of Demand occur?

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• If the price goes down for a product, the purchasing power increases for consumers -allowing them to purchase more.– Investopedia video clip

2. The Income Effect

Why does the Law of Demand occur?

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• First, let’s define the words:– Diminishing= Decreasing– Marginal=One additional unit– Utility = Satisfaction

• So, the law of diminishing marginal utility states that as you consume anything, the additional satisfaction that you will receive will eventually start to decrease

• In other words, the more you buy of ANY GOOD the less satisfaction you get from each new unit consumed.

3. Law of Diminishing Marginal Utility

Why does the Law of Demand occur?

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Discussion Questions:1. What does this have to do with the Law of Demand?2. How does this effect the pricing of businesses?

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Law of Diminishing Marginal Utility-Investopedia video clip

Can you see the Law of Diminishing Marginal Utility in Disneyland’s pricing strategy?

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2010 Question 36

Graphing Demand

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The Demand Curve• A demand curve is a graphical representation

of a demand schedule.• The demand curve is downward sloping

showing the inverse relationship between price (on the y-axis) and quantity demanded (on the x-axis)

• When reading a demand curve, assume all outside factors, such as income, are held constant. (This is called ceteris paribus)

Let’s draw a new demand curve for milk…

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GRAPHING DEMAND

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

Draw this large in your notes

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PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80

GRAPHING DEMAND

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80Demand

Where do you get the Market Demand?

Q

Billy Price Q Demd

$5 1

$4 2

$3 3

$2 5

$1 7

Jean Other Individuals Price Q Demd

$5 0

$4 1

$3 2

$2 3

$1 5

Price Q Demd

$5 9

$4 17

$3 25

$2 42

$1 68

Price Q Demd

$5 10

$4 20

$3 30

$2 50

$1 80

Market

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P

Q2

P

Q25

P

Q30

P

$3 $3 $3 $3

D DDD

Demand Review1. What are the two key aspects of the definition of demand?2. What is the Law of Demand?3. Give an example of the substitution effect4. Give an example of the income effect5. Give an example of the law of diminishing marginal utility6. Explain how the law of diminishing marginal utility causes

the law of demand7. How do you determine the MARKET demand for a

particular good? 8. Name 10 fast food places

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Shifts in Demand• Ceteris paribus-“all other things held constant.”• When the ceteris paribus assumption is dropped,

movement no longer occurs along the demand curve. Rather, the entire demand curve shifts.

• A shift means that at the same prices, more people are willing and able to purchase that good.

This is a change in demand, not a change in quantity demanded

PRICE DOESN’T SHIFT THE CURVE

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Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80Demand

What if milk makes you smarter?

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80Demand

What if milk makes you smarter?

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

20

PriceQuantity

Demanded

$5 10 30

$4 20 40

$3 30 50

$2 50 70

$1 80 100Demand

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10 30

$4 20 40

$3 30 50

$2 50 70

$1 80 100Demand

D1

Increase in DemandPrices didn’t change but people want MORE Milk

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80

Demand

What if milk makes causes

baldness?

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80

Demand

What if milk makes causes

baldness?

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10 0

$4 20 5

$3 30 20

$2 50 30

$1 80 60

Demand

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

25

PriceQuantity

Demanded

$5 10 0

$4 20 5

$3 30 20

$2 50 30

$1 80 60

DemandD2

Decrease in DemandPrices didn’t change but people want LESS Milk

Change in Demand

Q

$5

4

3

2

1

Price of Milk

Quantity of Milk

Demand Schedule

10 20 30 40 50 60 70 80

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PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80

Demand

What happens to the demand for milk if

the price of milkgoes up?

NOTHING!The demand

stays the same

P

Q Milk

$3

$2

D1

Price of Milk

Quantity of Milk

10 20

Change in Qd vs. Change in Demand

A C

B

There are two ways to increase quantity from 10 to 20

D2

1. A to B is a change in quantity demand (due to a change in price)

2. A to C is a change in demand (shift in the curve)

What Causes a Shift in Demand?

5 Shifters (Determinates) of Demand:

– Tastes and Preferences– Income– Number of Buyers in the Market– Future Expectations of Price– Price of Related Goods

Changes in PRICE don’t shift the curve. It only causes movement along the curve.

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1. 1. Tastes or PreferencesTastes or Preferences

2. Income2. Income

2. Inferior Goods – Ex: Top Ramen, used cars, used clothes – As income increases, demand falls– As income falls, demand increases

1. Normal Goods – Ex: Luxury cars, Sea Food, jewelry, homes– As income increases, demand increases– As income falls, demand falls

The incomes of consumer change the demand, but how depends on the type of good.

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3. 3. Number of Buyers in the MarketNumber of Buyers in the Market

• The demand for a good in a particular market area is related to the number of buyers in the area

Description:– The more buyers, the higher the demand

– The fewer buyers, the lower the demand

4. 4. Expectations of Future PriceExpectations of Future PriceDescription:•Buyers who expect the price of a good to be higher in the future may buy the good NOW, thus increasing the current demand•Buyers who expect the price of a good to be lower in the future may WAIT until the future to buy the good, thus decreasing the current demand for the good

5. Prices of Related Goods5. Prices of Related Goods

2. Complements are two goods that are bought and used together. – Ex: If price of hot dogs falls, demand for hot dog

buns will... – If the price of one increase, the demand for the

other will fall. (or vice versa)

1. Substitutes are goods used in place of one another. – Ex: If price of Pepsi falls, demand for coke will…– If the price of one increases, the demand for the

other will increase (or vice versa)

The demand curve for one good can be affected by a change in the price of ANOTHER related good.

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1. Which of the following will cause the demand for milk to decrease?A.Increase in the price of a substitute B.A decrease in income assuming that milk is a normal goodC.A decrease in the price of milkD.An increase in the price of milkE.A decrease in the price of a complementary good

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Practice Questions

2. Which of the following will cause the quantity demanded of milk to decrease?A.Increase in the price of a substitute B.A decrease in income assuming that milk is a normal goodC.A decrease in the price of milkD.An increase in the price of milkE.A decrease in the price of a complementary good

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Practice Questions

• Draw nine demand curves

• Let the practicing commence!

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aspirin Variable that caused the shift:

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E-cigarettes

Variable that caused the shift:

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Printer cartridges

Variable that caused the shift:

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Variable that caused the shift:Normal Goods

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US accepts 10,000 Syrian refugees

Fresh vegetables

Variable that caused the shift:

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Movie ticketsVariable that caused the shift:

Movie tickets increase in price

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Bomb shelters

Variable that caused the shift:

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Ground beef

Variable that caused the shift:

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Variable that caused the shift:

Dinner Rolls

On Sale now for

$3.99

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The price of chainsaws decreases...

Jason Masks

Variable that caused the shift:

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Practice

Hamburgers (a normal good)1. Population boom 2. Incomes fall due to recession3. Price of tacos, a substitute, decreases4. Price increases to $5 for hamburgers5. New health craze- “No ground beef”6. Hamburger restaurants announce that they will significantly increase prices NEXT month 7. Price of fries, a complement, increases8. Restaurants lower price of burgers to $.50

Identify the determinant (shifter) then decide if demand will increase or decrease

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