unit 2: demand, supply, and consumer...

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: You are able to purchase diapers, but if you

aren’t willing to buy then there is NO demand)

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

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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 effect3.The Law of Diminishing Marginal

Utility We will define and explain each…

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

1. The Substitution Effect

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

2. The Income Effect

Why does the Law of Demand occur?

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• Utility = Satisfaction• We buy goods because we get utility from them• 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.

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

3. Law of Diminishing Marginal UtilityWhy does the Law of Demand occur?

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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

12

PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80

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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

13

PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80Demand

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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

3

P

Q2

P

Q25

P

Q30

P

$3 $3 $3 $3D DDD

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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? (from reading)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 CURVE16Copyright

ACDC Leadership 2015

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

17

PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80Demand

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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

18

PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80Demand

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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

19

PriceQuantity

Demanded

$5 10 30

$4 20 40

$3 30 50

$2 50 70

$1 80 100Demand

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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

20

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

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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

21

PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80

Demand

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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

22

PriceQuantity

Demanded

$5 10

$4 20

$3 30

$2 50

$1 80

Demand

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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

23

PriceQuantity

Demanded

$5 10 0

$4 20 5

$3 30 20

$2 50 30

$1 80 60

Demand

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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

24

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

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P

Q Milk

$3

$2

D1

Price of Milk

Quantity of Milk10 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)

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What Causes a Shift in Demand?

5 Shifters (Determinates) of Demand:

1.Number of Buyers2.Income and Wealth3.Tastes and Preferences4.Future Expectations5.Price of Related Goods

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

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Number of buyers in the market

• When a population increases or decreases demand curves will shift accordingly

Income and Wealth

• Income is the amount of money received each year from working, interest on savings, and other sources such as gifts.•A normal good is a good whose demand increases if income rises.•An inferior good is a good whose demand decreases if income rises.

Normal Good examples

Inferior Good examples

Inferior Goods

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Income and Wealth

• Wealth is the value of accumulated past savings, including human wealth.

Tastes• Tastes (or

preferences) are people’s underlying likes and dislikes.

Usefulness

• A good’s usefulness is its benefit in creating the products people ultimately want.

Expectations of Buyers

• When buyers sense prices will rise or fall quickly they will choose to act or not act

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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Substitutes

• Email v. Post Office• Margarine v. Butter• Pepsi v. Coke• Skis v. Snowboards

Substitutes

38

Substitutes

39

Substitutes

40

Substitutes

41

Substitutes

42

Substitutes

43

Substitutes

44

Substitutes

45

Complements

• Skis and ski boots• Tennis rackets and tennis balls• Peanut butter and jelly

Complements

47

48

Substitutes or Complements?

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 good49

Practice Questions

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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 good50

Practice Questions

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1. The income of the Pago-Pagans declines after a typhoon hits the island.

Quantity

Price

DD1

2. Pago-Pagan is named on of the most beautiful islands in the world and tourism to the island

doubles.

Quantity

Price

DD1

3. The price of Frisbees decreases. (Frisbees are a substitute good for boomerangs)

Quantity

Price

DD1

4. The price of boomerang t-shirts decreases, which I assume all of you know are a complementary good.

Quantity

Price

D

D1

5. The Boomerang Manufactures decide to add a money back guarantee on their product, which increases the

popularity for them.

Quantity

Price

D

D1

6. Many Pago-pagans begin to believe that they may lose their jobs in the near future. (Think

expectations!)

Quantity

Price

DD1

Practice

57

Shifter Increase or Decrease Left or Right

12345678

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

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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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