1. 4 The Market Forces of Supply and Demand CHAPTER
This is perhaps the most important chapter in the textbook. It’s worth mentioning to your students that investing extra time to master this chapter will make it easier for them to learn much of the subsequent material in the book.
This is also one of the longest chapters in the textbook, and this PowerPoint file is one of the most graph-intensive. Many students taking economics for the first time have difficulty grasping the graphs, which are critically important in this and all subsequent chapters in the book. So an extra degree of hand-holding might be appropriate.
Accordingly, this PowerPoint has carefully detailed animations that build many of the graphs with great care. For example, we show a demand or supply schedule next to the axes, and highlight each coordinate pair in the table as the corresponding point appears on the graph.
Please be assured that the presentation of graphs is more streamlined in subsequent chapters. In this early chapter, though, we do not want to leave any students behind.
If your students are already very comfortable with scatter-type graphs, consider simplifying or turning off the animation on these slides in order to get through them faster.
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2. Look for the answers to these questions
What factors affect buyers’ demand for goods?
What factors affect sellers’ supply of goods?
How do supply and demand determine the price of a good and the quantity sold?
How do changes in the factors that affect demand or supply affect the market price and quantity of a good?
How do markets allocate resources?
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

3. Markets and Competition
A group of buyers and sellers of a particular good or service
Buyers as a group
Determine the demand for the product
Sellers as a group
Determine the supply of the product
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4. Markets and Competition
Competitive market
Many buyers and many sellers, each has a negligible impact on market price
Perfectly competitive market
All goods are exactly the same
Buyers and sellers are so numerous that no one can affect the market price, “Price takers”
In the real world, there are relatively few perfectly competitive markets. Most goods come in lots of different varieties—including ice cream, the example in the textbook. And there are many markets in which the number of firms is small enough that some of them have the ability to affect the market price.
For now, though, we look at supply and demand in perfectly competitive markets, for two reasons: First, it’s easier to learn. Understanding perfectly competitive markets makes it a lot easier to learn the more realistic but complicated analysis of imperfectly competitive markets. Second, despite the lack of realism, the perfectly competitive model can teach us a lot about how the world works, as we will see many times in the chapters that follow.
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5. Demand Quantity demanded Law of demand
Amount of a good that buyers are willing and able to purchase
Law of demand
Other things equal
When the price of a good rises, the quantity demanded of the good falls
When the price falls, the quantity demanded rises
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

6. Quantity of lattes demanded
Sam’s Demand Schedule
Demand schedule:
A table, shows the relationship between the price of a good and the quantity demanded
Example: Sam’s demand for lattes
Notice that Sam’s preferences obey the law of demand.
Price of lattes
Quantity of lattes demanded
$0.00 16
1.00 14
2.00 12
3.00 10
4.00 8
5.00 6
6.00 4
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

7. Sam’s Demand Schedule and Demand Curve
Price of lattes
Quantity of lattes demanded
$0.00 16
1.00 14
2.00 12
3.00 10
4.00 8
5.00 6
6.00 4
Price of Lattes
Quantity of Lattes
Demand shows the relationship between the price of a good and quantity demanded. It can be represented with:
- A demand schedule: a table
- A demand curve: a graph (with price on the vertical axis and quantity on the horizontal axis)
Helen’s demand is the individual demand (an individual’s demand for a product)
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

8. Demand
Market demand
Sum of all individual demands for a good or service
Market demand curve: sum the individual demand curves horizontally
To find the total quantity demanded at any price, we add the individual quantities
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

9. Market Demand versus Individual Demand
Suppose Sam and Dean are the only two buyers in the market for lattes. (Qd = quantity demanded)
$0.00
6.00
5.00
4.00
3.00
2.00
1.00
Price 4 6 8 10 12 14 16
Sam’s Qd 2 3 4 5 6 7 8
Dean’s Qd
Market Qd + = 24 + = 21 + = 18 + = 6 9 12 15
This example violates the “many buyers” condition of perfect competition. Yet, we are merely trying to show here that, at each price, the quantity demanded in the market is the sum of the quantity demanded by each buyer in the market. This holds whether there are two buyers or two million buyers. But it would be harder to fit data for two million buyers on this slide, so we settle for two.
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10. The Market Demand Curve for LattesP P
Qd (Market)
$0.00 24
1.00 21
2.00 18
3.00 15
4.00 12
5.00 9
6.00 6 Q
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

11. Demand Curve Shifters The demand curve
Shows how price affects quantity demanded, other things being equal
These “other things” are non-price determinants of demand
Things that determine buyers’ demand for a good, other than the good’s price
Changes in them shift the D curve…
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

12. Demand Curve Shifters Number of buyers Increase in # of buyers
Increases quantity demanded at each price
Shifts D curve to the right
Decrease in # of buyers
Decreases quantity demanded at each price
Shifts D curve to the left
Income is the first demand shifter discussed in this chapter of the textbook. I chose to start with a different one (number of buyers), for the following reason:
In discussing the impact of changes in income on the demand curve, the textbook also introduces the concept of normal goods and inferior goods. Students may find it easier to learn about curve shifts if the presentation focuses solely on a curve shift (at least initially) without simultaneously introducing other concepts.
If you wish to present the demand shifters in the same order as they appear in the book, simply reorder the slides in this presentation.
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13. Demand Curve Shifters: # of BuyersP Q
Suppose the number of buyers increases.
Then, at each P, Qd will increase (by 5 in this example).
Beginning economics students often have trouble understanding the difference between a movement along the curve and a shift in the curve. Here, the animation has been carefully designed to help students see that a shift in the curve results from an increase in quantity at each price.
(A more realistic scenario would involve a non-parallel shift, where the horizontal distance of the shift would be greater for lower prices than higher ones. However, to remain consistent with the textbook, and to keep things simple, this slide shows a parallel shift.)
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14. Demand Curve Shifters Income Normal good, other things constant
An increase in income leads to an increase in demand: Shifts D curve to the right
Inferior good, other things constant
An increase in income leads to a decrease in demand: Shifts D curve to the left
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15. Demand Curve Shifters Prices of related goods, substitutes
Two goods are substitutes if
An increase in the price of one leads to an increase in the demand for the other
Example: pizza and hamburgers
An increase in the price of pizza increases demand for hamburgers, shifting hamburger demand curve to the right
Other examples:
Coke and Pepsi, laptops and tablets, music CDs and music downloads
If you are willing to spend a couple extra minutes on substitutes and complements, and have a blackboard or whiteboard to draw on, here’s an idea:
Before (or instead of) showing this slide, draw the demand curve for hamburgers. Pick a price, say $5, and draw a horizontal line at that price, extending from the vertical axis through the D curve and continuing to the right. Suppose Q = 1000 when P = $5. Label this on the horizontal axis.
Now ask your students: If pizza becomes more expensive, but price of hamburgers does not change, what would happen to the quantity of hamburgers demanded? Would it remain at 1000, would it increase, or would it decrease? Explain.
Some and perhaps most students will see right away that people will want more hamburgers when the price of pizza rises. After establishing this, note that the increase in the price of pizza caused an increase in the quantity demanded of hamburgers. Then state the term “substitutes” and give the definition.
Before giving the other examples (listed in the last bullet of this slide), do a similar exercise to develop the concept of complements. Finally, give the examples of substitutes and complements from the last bullet point of this and the following slide, but mix up the order and ask students to identify whether each example is complements or substitutes.
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16. Demand Curve Shifters Prices of related goods, complements
Two goods are complements if
An increase in the price of one leads to a decrease in the demand for the other
Example: computers and software
If price of computers rises, people buy fewer computers, and therefore less software; Software demand curve shifts left
Other examples:
College tuition and textbooks, bagels and cream cheese, eggs and bacon
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

17. Demand Curve Shifters Tastes
Anything that causes a shift in tastes toward a good will increase demand for that good and shift its D curve to the right
Example:
The Atkins diet became popular in the ’90s, caused an increase in demand for eggs, shifted the egg demand curve to the right
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

18. Demand Curve Shifters Expectations about the future
Expect an increase in income, increase in current demand
Expect higher prices, increase in current demand
Example:
If people expect their incomes to rise, their D for meals at expensive restaurants may increase now
Additional example: If the economy sours and people worry about their future job security, D for new cars may fall now
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

19. Summary: Variables That Influence Buyers
Students should notice that the only determinant of quantity demanded that causes a movement along the curve is price. Also notice: price is one of the variables measured along the axes of the graph.
Here’s a handy rule of thumb students can use to remember whether the curve shifts: If the variable causing demand to change is measured on one of the axes, you move along the curve. If the variable that’s causing demand to change does not appear on either axis, then the curve shifts.
This rule of thumb works with all curves in economics that involve an X-Y relationship, including the supply curve, the marginal cost curve, the IS and LM curves (not covered in this book), and many others, though it does not apply to curves drawn on time series graphs.
For an interesting break, you can discuss the case study ‘Two ways to reduce the quantity of smoking demanded’ on how to reduce smoking:
1. Use public service announcements, mandatory health warnings on cigarette packages, and prohibition of cigarette advertising on television to decrease the demand for cigarettes and other tobacco products.
2. Tax the manufacturer, and decreasing the quantity demanded (movement along demand curve). Studies showed:
10% ↑ in price → 4% ↓ in smoking
Teenagers: 10% ↑ in price → 12% ↓ in smoking
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20. Active Learning 1 Demand curve
Draw a demand curve for music downloads
What happens to it in each of the following scenarios?
Why?
The price of iPods falls
The price of music
downloads falls
The price of music CDs falls
In each case, there are only three possible answers:
- The curve shifts to the right
- The curve shifts to the left
- The curve does not shift (though there may be a movement along the curve)
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21. Active Learning 1 A. The price of iPods falls
Music downloads and iPods are complements.
A fall in price of iPods shifts the demand curve for music downloads to the right.
Price of music down-loads
Quantity of music downloads D1 D2 P1 Q1 Q2
Point out to your students that there are no numbers or units on either axis, and we are using “P1” and “Q1” to represent the initial price and quantity, rather than specific numerical values. Tell them that this is common, because in much economic analysis, the goal is only to see the direction of changes, not specific amounts. (Besides, if we put numbers on this graph, they’d just have been made up, so why bother?)
Also point out the following:
The price of music downloads is the same, but the quantity demanded is now higher. In fact, this is the nature of a shift in a curve: at any given price, the quantity is different than before.
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22. Active Learning 1 B. The price of music downloads falls
The D curve does not shift.
Move down along curve to a point with lower P, higher Q.
Price of music down-loads P1 Q2 P2 D1 Q1
Quantity of music downloads
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23. Active Learning 1 C. The price of music CDs falls
Music CDs and music downloads are substitutes.
A fall in the price of music CDs shifts demand for music downloads to the left.
Price of music down-loads D1 D2 P1 Q1 Q2
Quantity of music downloads
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24. Supply Quantity supplied Law of supply Amount of a good
Sellers are willing and able to sell
Law of supply
Other things equal
When the price of a good rises, the quantity supplied of the good rises
When the price falls, the quantity supplied falls
Supply comes from the behavior of sellers.
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25. Starbucks’ Supply Schedule
A table, shows the relationship between the price of a good and the quantity supplied.
Example: Starbucks’ supply of lattes
Notice that Starbucks’ supply schedule obeys the law of supply
Price of lattes
Quantity of lattes supplied
$0.00
1.00 3
2.00 6
3.00 9
4.00 12
5.00 15
6.00 18
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26. Starbucks’ Supply Schedule and Supply Curve
Price of lattes
Quantity of lattes supplied
$0.00
1.00 3
2.00 6
3.00 9
4.00 12
5.00 15
6.00 18 P
Supply shows the relationship between the price of a good and quantity supplied. It can be represented with:
- A supply schedule: a table
- A supply curve: a graph (with price on the vertical axis and quantity on the horizontal axis)
Starbucks’ supply is the individual supply(an individual producer’s supply for a product) Q
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27. Market Supply vs. Individual Supply
Sum of the supplies of all sellers of a good or service
Market supply curve: sum of individual supply curves horizontally
To find the total quantity supplied at any price, we add the individual quantities
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28. Market Supply vs. Individual Supply
Suppose Starbucks and Peet’s are the only two sellers in this market. (Qs = quantity supplied) 18 15 12 9 6 3
Qs Starbucks 12 10 8 6 4 2
Qs Peet’s
$0.00
6.00
5.00
4.00
3.00
2.00
1.00
Price
Market Qs + = + = 5 + = 10 + = 30 25 20 15
Again, the assumption of only two sellers is a clear violation of perfect competition. However, it’s much easier for students to learn how the market supply curve relates to individual supplies in the two-seller case.
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29. The Market Supply Curve
QS (Market)
$0.00
1.00 5
2.00 10
3.00 15
4.00 20
5.00 25
6.00 30 P Q
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30. Supply Curve Shifters The supply curve These “other things”
Shows how price affects quantity supplied, other things being equal
These “other things”
Are non-price determinants of supply
Changes in them shift the S curve…
“Non-price determinants of supply” simply means the things—other than the price of a good—that determine sellers’ supply of the good.
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

31. Supply Curve Shifters Input prices
Supply is negatively related to prices of inputs
Examples of input prices: wages, prices of raw materials
A fall in input prices makes production more profitable at each output price
Firms supply a larger quantity at each price
The S curve shifts to the right
“Output price” just means the price of the good that firms are producing and selling. I have used “output price” here to distinguish it from “input prices.”
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32. Supply Curve Shifters: Input PricesQ
Suppose the price of milk falls.
At each price, the quantity of lattes supplied will increase (by 5 in this example).
Again, the animation here is carefully designed to help make clear that a shift in the supply curve means that there is a change in the quantity supplied at each possible price. If it seems tedious, you can turn it off.
In any case, be assured that, by the end of this chapter, the animation of curve shifts will be streamlined and simplified.
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33. Supply Curve Shifters Technology Number of sellers
Determines how much inputs are required to produce a unit of output
A cost-saving technological improvement has the same effect as a fall in input prices, shifts S curve to the right
Number of sellers
An increase in the number of sellers
Increases the quantity supplied at each price
Shifts S curve to the right
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34. Supply Curve Shifters Expectations about future
Example: Events in the Middle East lead to expectations of higher oil prices
Owners of Texas oilfields reduce supply now, save some inventory to sell later at the higher price
S curve shifts left
Sellers may adjust supply* when their expectations of future prices change (*If good not perishable)
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

35. Summary: Variables That Influence Sellers
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36. Active Learning 2 Supply curve
Draw a supply curve for tax return preparation software. What happens to it in each of the following scenarios?
Retailers cut the price of the software.
A technological advance allows the software to be produced at lower cost.
Professional tax return
preparers raise the price of
the services they provide.
“Tax return preparation software” means programs like TurboTax by Quicken and TaxCut by H&R Block.
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

37. Active Learning 2 A. Fall in price of tax return software
S curve does not shift.
Move down along the curve to a lower P and lower Q.
Price of tax return software
Quantity of tax return software S1 P1 Q1 Q2 P2
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

38. Active Learning 2 B. Fall in cost of producing software
S curve shifts to the right:
at each price, Q increases.
Price of tax return software S2 S1 P1 Q2 Q1
Quantity of tax return software
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

39. Active Learning 2 C. Professional preparers raise their price
Price of tax return software
Quantity of tax return software S1
Trick question:
This shifts the demand curve for tax preparation software, not the supply curve.
Professional tax prepares are a substitute for a tax preparation software (we use at home). A change in the price of a good will shift the demand for the substitute.
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

40. Supply and Demand TogetherQ
Equilibrium: Price has reached the level where quantity supplied equals quantity demanded D S
In equilibrium, various forces are in balance. A situation in which market price has reached the level where Quantity supplied = Quantity demanded; where supply and demand curves intersect
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41. Supply and Demand Together
Equilibrium price: price where Q supplied = Q demanded
Equilibrium quantity: Q supplied and demanded at the equilibrium price P Q D S P QD QS $0 24 1 21 5 2 18 10 3 15 4 12 20 9 25 6 30
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42. ASK THE EXPERTS Price Gouging
“Connecticut should pass its Senate Bill 60, which states that during a ‘severe weather event emergency, no person within the chain of distribution of consumer goods and services shall sell or offer to sell consumer goods or services for a price that is unconscionably excessive.’”
In the textbook, the ‘In the news’ article about price gouging explains why price gouging is unpopular with politicians and people affected by natural disasters. “When a disaster such as a hurricane strikes a region, many goods experience an increase in demand or a decrease in supply, putting upward pressure on prices. Policymakers often object to these price hikes, but this opinion piece endorses the market’s natural response.”
This ‘Ask the experts’ feature provides the opportunity for class discussion.
Start by asking the class what they know about natural disasters, and how are people (households, firms, and the government) reacting to them.
After showing the statement, you can ask your students to choose one of the options: agree, disagree, or uncertain. You can collect their answers in a variety of ways: show of hands, ballot, clicker system, etc. If time permits, you can allow students to group and discuss some of the reasons they chose their answer.
Ask the students to share with the class their reasons. Their answers will vary.
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43. Markets Not in Equilibrium: Surplus
Surplus (excess supply):
quantity supplied is greater than quantity demanded
Example: if P = $5,
then QD = 9 lattes
and QS = 25 lattes
resulting in a surplus of 16 lattes P Q S D
Surplus
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44. Markets Not in Equilibrium: Surplus
Facing a surplus, sellers try to increase sales by cutting price.
This causes QD to rise
and QS to fall…
…which reduces the surplus. P Q S D
Surplus
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45. Markets Not in Equilibrium: Surplus
Facing a surplus, sellers try to increase sales by cutting price.
This causes QD to rise
and QS to fall…
Prices continue to fall until market reaches equilibrium. P Q S D
Surplus
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46. Markets Not in Equilibrium: Shortage
Shortage (excess demand):
quantity demanded is greater than quantity supplied
Example: if P = $1,
then QD = 21 lattes
and QS = 5 lattes
resulting in a shortage of 16 lattes P Q S D
Shortage
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

47. Markets Not in Equilibrium: Shortage
Facing a shortage, sellers raise the price,
causing QD to fall
and QS to rise,
…which reduces the shortage. P Q S D
Shortage
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48. Markets Not in Equilibrium: Shortage
Facing a shortage, sellers raise the price,
causing QD to fall
and QS to rise,
…which reduces the shortage.
Prices continue to rise until market reaches equilibrium. P Q S D
Shortage
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

49. Supply and Demand Together
Three steps to analyzing changes in equilibrium
Decide whether the event shifts the supply curve, the demand curve, or, in some cases, both curves
Decide whether the curve shifts to the right or to the left
Use the supply-and-demand diagram
Compare the initial and the new equilibrium
Effects on equilibrium price and quantity
Step 1 requires knowing all of the things that can shift D and S—the non-price determinants of demand and of supply.
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50. EXAMPLE: The Market for Hybrid CarsQ
price of hybrid cars S1 D1 P1 Q1
quantity of hybrid cars
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51. EXAMPLE 1: A Shift in Demand
EVENT TO BE ANALYZED: Increase in the price of gas.
STEP 1: D curve shifts
because price of gas affects demand for hybrids. (S curve does not shift, because price of gas does not affect cost of producing hybrids)
STEP 2: D shifts right
because high gas price makes hybrids more attractive relative to other cars.
STEP 3: The shift causes an increase in price and quantity of hybrid cars. P Q S1 D2 D1 P2 Q2 P1 Q1
Notice: When P rises, producers supply a larger quantity of hybrids, even though the S curve has not shifted.
Always be careful to distinguish b/w a shift in a curve and a movement along the curve.
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

52. Shift vs. Movement Along Curve
Change in supply:
A shift in the S curve
Occurs when a non-price determinant of supply changes (like technology or costs)
Change in the quantity supplied:
A movement along a fixed S curve
Occurs when P changes
Remind your class often the difference between movements along a curve (change in quantity caused by a change in price) and shifts (caused by changes in the non-price determinants).
“Supply” refers to the position of the supply curve, while “quantity supplied” refers to the specific amount that producers are willing and able to sell at a specific price.
If you’d like to be a rebel, delete this slide and the next and all references to the jargon it contains, and just use the terms “movement along a curve” and “shift in a curve.” Note, however, that this is not the official recommendation of Cengage Learning or Dr. Mankiw.
If you’d like to cover this slide but make it move more quickly, for this slide and the next, delete the text starting with “occurs when” and give the information to your students verbally or rely on them to read it in the textbook.
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53. Shift vs. Movement Along Curve
Change in demand:
A shift in the D curve
Occurs when a non-price determinant of demand changes (like income or # of buyers)
Change in the quantity demanded:
A movement along a fixed D curve
Occurs when P changes
Similarly, “demand” refers to the position of the demand curve, while “quantity demanded” refers to the specific amount that consumers are willing and able to buy at a specific price.
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

54. EXAMPLE 2: A Shift in Supply
EVENT: New technology reduces cost of producing hybrid cars.
STEP 1: S curve shifts because event affects cost of production. (D curve does not shift, because production technology is not one of the factors that affect demand)
STEP 2: S shifts right because event reduces cost, makes production more profitable at any given price.
STEP 3: The shift causes price to fall and quantity to rise. P Q S1 S2 D1 P1 Q1 P2 Q2
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55. EXAMPLE 3: A Shift in Both Supply and Demand
EVENTS: Price of gas rises AND new technology reduces production costs
STEP 1: Both curves shift.
STEP 2: Both shift to the right.
STEP 3: Q rises, but the effect on P is ambiguous:
If demand increases more than supply, P rises. P Q S1 S2 D2 D1 P2 Q2 P1 Q1
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

56. EXAMPLE 3: A Shift in Both Supply and Demand
EVENTS: Price of gas rises AND new technology reduces production costs
STEP 3: Q rises, but the effect on P is ambiguous:
But if supply increases more than demand, P falls. P Q S1 S2 D2 D1 P1 Q1 P2 Q2
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

57. Active Learning 3 Shifts in supply and demand
Use the three-step method to analyze the effects of each event on the equilibrium price and quantity of music downloads. Event A: A fall in the price of music CDs Event B: Sellers of music downloads negotiate a reduction in the royalties they must pay for each song they sell. Event C: Events A and B both occur.
Important note about Event B:
The royalties that sellers must pay the artists are part of sellers’ “costs of production.” Typically, this royalty is a fixed amount each time one of the artist’s songs is downloaded. Event B, therefore, describes a reduction in sellers’ “costs of production.”
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58. Active Learning 3 A. A fall in the price of music CDs
The market for music downloads
STEPS:
1. D curve shifts
2. D curve shifts left
3. P and Q both fall P Q S1 D2 D1 P1 Q1 P2 Q2
This is an extension of Active Learning exercise 1C, where we saw that a fall in the price of music CDs would cause a fall in demand for music downloads, because the two goods are substitutes.
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59. Active Learning 3 B. Fall in cost of royalties
STEPS:
S curve shifts
(Royalties are part of sellers’ costs)
2. S curve shifts right
3. P falls, Q rises
The market for music downloads P Q S1 S2 D1 P1 Q1 Q2 P2
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

60. Both curves shift (see parts A & B) D shifts left, S shifts right
Active Learning 3 C. Fall in price of music CDs and fall in cost of royalties
STEPS:
Both curves shift (see parts A & B)
D shifts left, S shifts right
P falls.
Effect on Q is ambiguous: the fall in demand reduces Q, the increase in supply increases Q.
It’s not necessary to draw a graph here. The answers to steps 1 and 2 should be clear from parts A and B. The answer to step 3 is a combination of the results from A and B.
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61. How Prices Allocate Resources
“Markets are usually a good way to organize economic activity”
In market economies
Prices adjust to balance supply and demand
These equilibrium prices
Are the signals that guide economic decisions and thereby allocate scarce resources
In the textbook, the conclusion of this chapter offers some very nice elaboration on the third bullet point.
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62. Summary
Economists use the model of supply and demand to analyze competitive markets.
Many buyers and sellers, all are price takers
The demand curve shows how the quantity of a good demanded depends on the price.
Law of demand: as the price of a good falls, the quantity demanded rises; the D curve slopes downward
Other determinants of demand: income, prices of substitutes and complements, tastes, expectations, and number of buyers.
If one of these factors changes, the D curve shifts
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63. Summary
The supply curve shows how the quantity of a good supplied depends on the price.
Law of supply: as the price of a good rises, the quantity supplied rises; the S curve slopes upward.
Other determinants of supply: input prices, technology, expectations, and number of sellers.
If one of these factors changes, supply curve shifts.
The intersection of the supply and demand curves determines the market equilibrium.
At the equilibrium price, quantity demanded = quantity supplied
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

64. Summary
The behavior of buyers and sellers naturally drives markets toward their equilibrium.
When the market price is above the equilibrium price, there is a surplus of the good, which causes the market price to fall.
When the market price is below the equilibrium price, there is a shortage, which causes the market price to rise.
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.

65. Summary
To analyze how any event influences a market, we use the supply-and-demand diagram to examine how the event affects the equilibrium price and quantity.
Decide whether the event shifts the supply curve or the demand curve (or both).
Decide in which direction the curve shifts.
Compare the new equilibrium with the initial one.
In market economies, prices are the signals that guide economic decisions and thereby allocate scarce resources.
© 2018 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use.