1. Chapter 3 Where Prices Come From: The Interaction of Demand and Supply
Economics 2420
Chapter 3
Where Prices Come From: The Interaction of Demand and Supply

2. A. An Overview
Demand and supply are the two sides of the market for goods and services (factors of production also).
Demand and Supply are important because their interaction determines the prices of goods and services
Typically, demand reflects consumers’ behavior while supply reflects the producers’ behavior

3. B. The Demand Side of the Market
Quantity demanded - The quantity of a good or service that a consumer is willing to purchase at a given price.

4. Demand Curve for Printers
Price($)
175
150
125
100
D-curve 75 Q 3 4 5 6 7

5. Demand Schedule and Demand Curve
Notice that both the demand schedule (table) and curve (graph) show the relationship between the price and quantity demanded.
What is the nature of the relationship? Inverse.

6. The Law of Demand
2.The Law of Demand a. The Law of Demand shows an inverse price-quantity relationship i.e. as price decreases, qt demanded increases, and vice-versa, holding everything else constant
3. What are the justifications of the Law of Demand? Substitution effect The change in the quantity demanded of a good that results from a change in price making the good more or less expensive relative to other goods that are substitutes. Income effect The change in the quantity demanded of a good that results from the effect of a change in the good’s price on consumer purchasing power.
Law of Diminishing Marginal Utility (wait until chapter 9 in the text)

7. 4. Some Exceptions to the Law of Demand
The giffen-good case- As price increases, the quantity demanded increases (Potatoes in Ireland)
Bandwagon effect- People buy expensive goods to be like others- Air Nike Shoes
The snob effect- conspicuous consumption-expensive car to stand out

8. 5. Change in Quantity Demanded vs Change in Demand
ΔQ demanded- refers to a movement along the same demand curve due a price change only
Δ in Demand refers to the shift in the whole demand curve due to other factors than the price of the good

9. Change in Qty Demanded vs Change in Demand
Movement from A to C is change in Qt
demanded
A shift in D-curve from D0 to D1 or D2 is change in demand
Price A B C D1 D2 D0 Q

10. 6. Shifters (Determinants) of Demand
Δ Price of related goods
Substitutes Goods an d services that can be used for the same purpose P Coke  Dpepsi
Complements Goods that are used together. When price of one goes up, demand for
Δ Income
Normal good A good for which the demand increases as income rises and decreases as income falls (New Car).
Inferior good A good for which the demand increases as income falls, and decreases as income rises (Used car).
Δ Tastes (smoking and lung cancer; mad cow disease and demand for beef)
Δ Population and demographics (demand for housing and school as population increases
Demographics The characteristics of a population with respect to age, race, and gender.
Δ Expected future prices( current demand increases if prices are expected to rise in the future)

11. Change in Qty Demanded vs Change in Demand
Movement from A to C is change in Qt
demanded
A shift in D-curve from D0 to D1 or D2 is change in demand
Price A B C D1 D2 D0 Q

12. C. The Supply Side of the Market
8. Quantity supplied The quantity of a good or service that a firm is willing to supply at a given price.
Supply schedule A table that shows the relationship between the price of a product and the quantity of the product supplied.
Supply curve A curve that shows the relationship between the price of a product and the quantity of the product demanded.

13. The Supply Side of the Market
3- 6
Hewlett-Packard’s Supply Schedule and Supply Curve
S-Curve
Price
175
100 75 10 8
8.5

14. The Supply Side of the Market
9. Law of supply shows a positive price- quantity relationship, i.e. as price increases, qt supplied increases and vice- versa

15. 10. ΔQt Supplied and vs Δ in Supply
ΔQt Supplied refers to a movement along the same supply curve due to a change in product price Δ in Supply refers to a shift in the whole supply curve due to factors other than the product price

16. 11. Variables That Shift Supply
Δ in Price of inputs (labor cost, capital cost, etc.)
Δ in Technology
Improvement in technology reduces and increases supply (positive) and lack of it will increase cost and reduce supply (negative)
Δ in Prices of substitutes in production
Δ Expected future prices
Δ Number of firms in the market

17. Shifts in Supply S2 S0
Price $ S1
Increase
Decrease
(‘000) Q

18. D. Market Equilibrium: Putting Demand and Supply Together
12. Market equilibrium price -A situation where quantity demanded equals quantity supplied.
Competitive market equilibrium A market equilibrium with many buyers and many sellers.

19. Market Equilibrium: Putting Demand and Supply Together
The Effect of Surpluses and Shortages on the Market Price
Price S
Surplus
125
Pe=100 75 D Q
18.5
21.5
19.5 Qe

20. Price above and below Eq.
2. Surplus A situation in which the quantity supplied is greater than the quantity demanded.
3. Shortage A situation in which the quantity demanded is greater than the quantity supplied.

21. How does the market eliminate surpluses and shortages?
When price is set above the market eq. price, a surplus will occur; but it will be eliminated because competition will force sellers to accept lower and lower prices
When price is set below the market eq. price, a shortage will occur; but it will be eliminated because competition will force buyers higher and higher prices up the eq. price
At equilibrium, there are no surpluses, nor shortages!

22. Market Equilibrium
4. The market equilibrium price is important because it channels resources to their best use.
When consumers buy a good or service, they channel resources to the production of that good, or service
Price of DVD Production of DVDs by hiring workers, investing machines to make DVDs, etc.

23. 13. The Effect of Demand and Supply Shifts on Equilibrium
If demand increases and supply remains constant, then both eq. price and quantity will increase. Illustrate.
If supply increases (deceases) and demand remains the same, then eq. decreases (increases) and eq. qt increases (decreases). Illustrate.
If both demand and supply increase, then we cannot predict what happens to the eq. price. It depends on the price elasticity of demand and supply. Illustrate.