Chapter 2. Supply and Demand

Transcription

1 Chapter 2 Supply and Demand

2 Reading Assignment for the Week: Finish Chapter 2 Chapter Copyright 2012 Pearson Addison-Wesley. All rights reserved.

3 Topics 1. Demand. 2. Supply. 3. Market Equilibrium. 4. Shocking the Equilibrium. 5. Effects of Government Interventions. 6. When to Use the Supply-and-Demand Model. 2-3 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

4 Demand: Determinants of Demand The following factors determine the demand for a good: Price of the good Tastes Information Prices of other goods Complements and substitutes Income Government rules and regulations (taxes) Other factors 2-4 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

5 Demand: The Demand Curve Quantity demanded - the amount of a good that consumers are willing to buy at a given price, holding constant the other factors that influence purchases. Demand curve - the quantity demanded at each possible price, holding constant the other factors that influence purchases 2-5 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

6 p, $ per kg Figure 2.1 A Demand Curve Demand curve for pork, D 1 Law of Demand consumers demand more of a good the lower its price, holding constant all other factors that influence consumption Q, Million kg of pork per year 2-6 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

7 p, $ per kg Figure 2.2 A Shift of the Demand Curve Effect of a 60 increase in the price of beef 3.30 D 2 D Q, Million kg of pork per year 2-7 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

8 The Demand Function The processed pork demand function is: Q = D(p, p b, p c, Y) where Q is the quantity of pork demanded p is the price of pork (dollars per kg) p b is the price of beef (dollars per kg) p c is the price of chicken (dollars per kg) Y is the income of consumers (thousand dollars) 2-8 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

9 From the Demand Function to the Demand Curve Estimated demand function for pork: Q = p + 20p b + 3p c + 2Y Using the values p b = 4, p c = 3.33 and Y = 12.5, we have Q = p which is the linear demand function for pork. 2-9 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

10 p, $ per kg From the Demand Function to the Demand Curve (cont.) Q = p Demand curve for pork, D 1 If p = $3.30 then, In If If pgeneral, If decreases pp increases = 0, then by $1 by Q = 220 (to $1 $2.30) 286 (to $4.30) then, D Q = -20D p Q = 240 = then, slope D p Q = Q, Million kg of pork per year 2-10 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

11 Summing Demand Curves The total demand shows the total quantity demanded at each price The total quantity demanded at a given price is the sum of the quantity each consumer demands at that price Q = Q 1 + Q 2 = D 1 (p) + D 2 (p) 2-14 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

12 Application Aggregating the Demand for Broadband Service 2-15 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

13 Supply: Determinants of Supply The following factors determine the supply for a good: Price of the good Costs Government rules and regulations 2-16 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

14 Supply: The Supply Curve Quantity supplied - the amount of a good that firms want to sell at a given price, holding constant other factors that influence firms supply decisions, such as costs and government actions Supply curve - the quantity supplied at each possible price, holding constant the other factors that influence firms supply decisions 2-17 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

15 p, $ per kg Figure 2.3 A Supply Curve An increase in the price 5.30 Supply cu rve, S causes a movement along the curve and an increase in the quantity supplied. 300 Q, Million kg of pork per year 2-18 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

16 p, $ per kg Figure 2.4 A Shift of a Supply Curve A $0.25 increase in the price of hogs.. shifts the supply curve to the left S 2 S reducing the quantity supplied at the previous price Q, Million kg of pork per year 2-19 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

17 The Supply Function The processed pork supply function is: Q = S(p, p h ) where Q is the quantity of pork supplied p is the price of pork (dollars per kg) p h is the price of a hog (dollars per kg) 2-20 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

18 From the Supply Function to the Supply Curve Estimated supply function for pork: Q = p 60p h Using the values p h = $1.50 per kg Q = p. What happens to the quantity supplied if the price of processed pork increases by Δp = p 2 p 1? 2-21 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

19 Summing Supply Curves The total supply curve shows the total quantity produced by all suppliers at each price Horizontal sum of each producer s supply curve Sum of all quantities supplied at a given price 2-22 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

20 Figure 2.5 Total Supply: The Sum of Domestic and Foreign Supply 2-23 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

21 Market Equilibrium Equilibrium - a situation in which no one wants to change his or her behavior equilibrium price is the price at which consumers can buy as much as they want and sellers can sell as much as they want equilibrium quantity is the quantity bought and sold at the equilibrium price 2-26 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

22 Market Equilibrium (cont.) Excess demand the amount by which the quantity demanded exceeds the quantity supplied at a specified price. Excess supply the amount by which the quantity supplied is greater than the quantity demanded at a specified price 2-27 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

23 p, $ per kg Figure 2.6 Market Equilibrium Above the equilibrium price. Market equilibrium point! Excess supply = e S Below the equilibrium price. Excess demand = 39 is below the quantity demanded D is below the quantity supplied the quantity supplied the quantity demanded Q, Million kg of por k per year 2-28 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

24 Using Math to Determine the Equilibrium Demand: Q d = p Supply: Q s = p Equilibrium: Q d = Q s p = p 60p = 198 P = $3.30 Q = (3.3) = Copyright 2012 Pearson Addison-Wesley. All rights reserved.

25 Shocking the Equilibrium The equilibrium changes only if a shock occurs that shifts the demand curve or the supply curve. These curves shift if one of the variables we were holding constant changes (e.g., income, other prices, tastes & preferences, etc.) Copyright 2012 Pearson Addison-Wesley. All rights reserved.

26 p, $ per kg Figure 2.7a Equilibrium Effects of a Shift of a Demand Curve A $0.60 increase in the price of beef shifts demand outward Which puts an upward pressure on the price to a new equilibrium e 1 e 2 S D 2 Excess demand = 12 D 1 At the original price there is now excess demand Q, Million kg of pork per year 2-32 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

27 p, $ per kg Figure 2.7b Equilibrium Effects of a Shift of a Supply Curve A $0.25 increase in the price of hogs shifts the supply curve to the left Which puts an upward pressure on the price to a new equilibrium e 2 e 1 S 2 S 1 Excess demand = 15 D At the original price there is now excess demand Q, Million kg of pork per year 2-33 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

28 Equilibrium Effects of Government Interventions Government action can cause a shift in the supply curve, the demand curve, or both the quantity demanded to be different from quantity supplied 2-36 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

29 Equilibrium Effects of Government Interventions (cont.) Policies that shift supply curves Licensing laws, quotas Policies that cause demand to differ from supply Price ceilings: The maximum price at which the good can be sold at. Only effective if set below the equilibrium price. Price floors: This is the minimum price at which the good can be sold at. Only effective if set above the equilibrium price Copyright 2012 Pearson Addison-Wesley. All rights reserved.

30 Figure 2.8 A Ban on Rice Imports Raises the Price in Japan p, Price of rice per pound p 2 e 2 p 1 S (ban) A ban on rice imports shifts the total supply of rice in Japan e 1 S (no ban) which causes the equilibrium to change and the price to increase. Q 2 Q 1 D Q, Tons of rice per year 2-38 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

31 p, $ per gallon Figure 2.9 Price Ceiling on Gasoline Supply shifts to the left. S 1 but gas stations must continue to charge a price of p 1.. p 1 =p e 1 Price ceiling D which creates excess demand. Q s Excess demand Q 1 = Q d Q, Gallons of gasoline per month 2-41 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

32 Solved Problem 2.5 Suppose that there is a single labor market in which everyone is paid the same wage. If a binding minimum wage, w, is imposed, what happens to the equilibrium in this market? Answer: Show the initial equilibrium before the minimum wage is imposed. Draw a horizontal line at the minimum wage, and show how the market equilibrium changes Copyright 2012 Pearson Addison-Wesley. All rights reserved.

33 Figure 2.10 Price Floor Example (Minimum Wage) 2-43 Copyright 2012 Pearson Addison-Wesley. All rights reserved.

34 Why Supply Need Not Equal Demand The quantity that firms want to sell and the quantity that consumers want to buy at a given price need not equal the actual quantity that is bought and sold. Example: price ceiling Copyright 2012 Pearson Addison-Wesley. All rights reserved.