1. CDAE 254 - Class 15 Oct. 17 Last class: 4. Market demand and elasticity Quiz 4 Today: Result of Quiz 4 Review for the midterm exam Next class: Midterm exam Important dates: Problem set 4 due today Midterm exam (Chapters 1-4): Thursday, Oct. 19

2. Result of Quiz 4 N = 47Range = 3 – 10Average = 7.35

3. Class Exercise (Thursday, Oct. 5) For demand function Q = 28 - 2P, (a) What is the consumer surplus when the price (P) is equal to $6 per unit? (b) What is the change in consumer surplus when a sales tax of $1 per unit is added to the current price of $6 per unit?

4. 4. Market demand and elasticity 4.1. Market demand curves 4.2. A general definition of elasticity 4.3. Price elasticity of demand 4.4. Income elasticity of demand 4.5. Cross-price elasticity of demand 4.6. Empirical studies of demand 4.7. Applications

5. Chapter 4: Review questions (1)What is a market demand function (curve) and how to draw it from individual demand curves? (2)How does a change in income or the price of another commodity shift a market demand curve? (3)What is the general definition of elasticity and how to calculate it and how to interpret it? (4)How to calculate a price elasticity from (a) two observations and (b) a demand function? (5)What is the relation between price elasticity and total revenue and (market share)? (6)How to calculate an income elasticity from (a) two observations and (b) a demand function? (7)How to calculate a cross-price elasticity from (a) two observations and (b) a demand function? (8)How to examine the relation between two commodities according to their cross price elasticities?

6. 4.6. Cross-price elasticity of demand (1) Definition: The percentage change in the quantity demanded of a good (Q) in response to a 1% change in the price of another good.

7. 4.6. Cross-price elasticity of demand (2) How to calculate cross-price elasticities? (1) When we have two observations: e.g., the demand for pork increased from 100 to 110 when the price of beef increased from 3 to 3.6, what is the elasticity of pork demand with respect to beef price? (2) When we have a demand function: e.g., Q pork = 40 - 2 P pork + 0.5 P beef What is the elasticity of pork demand with respect to beef price when the pork price is 4 and beef price is 6?

8. Class Exercise (Tuesday, Oct. 12) For demand function Qc = 300 – 0.3Pc – 0.1Pp + 0.05 I, where Qc is the demand for laptop computers in a market, Pc is the average price of laptop computers, Pp is the average price of printers and I is the average income. If we know the average laptop computer price is $800, the average printer price is $100 and the average income is $20,000, calculate: (1) the income elasticity of demand for laptop computers: (2) the own-price elasticity of demand for laptop computers: (3) the cross-price elasticity of demand for laptop computers with respect to the average price of printers.

9. 4.7. Empirical studies of demand (1) Examples of estimated demand elasticities (2) Estimation of demand functions (regression analysis) (3) How to estimate demand elasticity from demand equation? (4) Elasticity matrix (e.g., demand for animal products in urban China)

10. Demand elasticities in urban China

11. Midterm exam 1. What will be covered in the exam? 2. What will be the format? 3. What are the study materials and practice problems? 4. What do you need to bring to the exam? 5. Suggestions

12. Midterm exam 1. What will be covered in the exam? -- Chapter 1 -- Chapter 4 -- Approximate distribution: Chapter 1 10 - 15% Chapter 2 25 - 30% Chapter 3 25 - 30% Chapter 4 30 - 35%

13. Midterm exam 2. What will be the format? -- Multiple-choice questions (about 45-50 points) (e.g., interpretation of an income elasticity of 0.4) -- Problems (about 25 - 35 points) (e.g., calculate a demand elasticity) -- Graphical analysis (about 15 - 25 points) (e.g., draw a demand curve and estimate CS)

14. Midterm exam 3. What are the study materials and practice problems? Quiz 1 to Quiz 4 Class exercises Class examples Lecture notes (class 01 -- class 15) Problem sets Textbook (Chapter 1 to Chapter 4)

15. Midterm exam 4. What do you need to bring to the exam? -- Your calculator -- A ruler will be helpful -- No formula sheet is needed

16. Midterm exam 5. Suggestions a. Go over each quiz and make sure you understand and know how to answer each question in each quiz b. Go over each class exercise and make sure you understand and know how to answer every question c. Go over the lecture notes, especially for the classes you missed d. Go over your problem sets and Chapters 1-4 of the textbook e. Study hard and feel confident!