1. A Primer on Demand Analysis and Market Equilibrium
Chapter 3 (Hirschey) pp

2. Key Concepts Demand Supply Market equilibrium Elasticity
A number of issues arise in the agribusiness environment that center attention on demand.

3. Consumer Demand or Customer Demand
Demand is the quantity of a good/service that customers (consumers) are willing and able to purchase during a specified period of time under a given set of economic conditions.
Derived from constrained utility (satisfaction) maximization

4. Demand Curve
The Demand Curve shows the theoretical relation between price and quantity demanded, holding all other factors constant.
Axes: price is on y-axis, quantity on the x-axis
Example: Demand curve for Lipton tea,
Q=2500 – 500P
Key question: How are these numbers obtained?

5. Demand Curve for Lipton Tea
Average price per package 5 4 3 2 1
Demand Curve
Q = 2,500 – 500P
P = 5 – .002Q
inverse demand
curve
packages of Lipton tea

6. Own-Price Effects
Movement along a given demand curve reflects a change in price and quantity of the commodity in question.
Answer the following question:
What happens to the quantity demanded if the price changes (exogenously) holding all other factors constant?
Law of demand:
The demand curve is negatively sloped.
An increase (a decrease) in own price leads to a decrease (an increase) in quantity demanded.
A very important empirical finding in economics.

7. Other Factors Affecting Demand
Prices of other products
Income
Advertising (positive information)
Food Recalls or Food Scares (negative information)
Health and nutrition factors
Lifestyle factors
Tastes and preferences

8. price of substitute product
Translations of the Theoretical Construct into a Quantitative Appraisal
1. Q = a-bP
2. Q = a0 – a1P + a2I + a3A + a4PS
The coefficients a0, a1, a2, a3, and a4 are labeled the demand parameters.
We expect certain signs and magnitudes of the demand parameters according to economic theory.
Different versions of the model for applied analysis are possible.
own-price effect
(-)
income effect
(+)
advertising
effect
(+)
price of substitute product
(+)

9. Demand Curve: Example

10. Shifts in Demand
Changes in any factors other than the product price lead to a shift of the demand curve.

11. Supply
Supply: quantity that a firm is willing and able to provide at a given price, holding other factors constant.
Factors affecting supply:
Price
Production costs
Technology
Government policy (e.g. price supports, taxes, subsidies, etc…)

12. Supply Curve
Supply curve shows the relation between price and the quantity supplied, holding all other factors constant.
Question: What happens to the quantity supplied if the product price changes?
No Law of Supply: supply curve can be upward/downward sloping, vertical, horizontal.
Change in the supply curve:
A change in the product price leads to a movement along the supply curve (change in quantity supplied).
A change in any factors other than the product price leads to a shift of the supply curve (change in supply).

13. Supply Curve (con’t.)

14. Market Equilibrium Supply = Demand Example: Automobile:
Supply: Qs = -42,000,000+2,000p
Demand: Qd = 20,500, p

15. Surplus, Shortage, and Market Equilibrium

16. Elasticity Concept: a measure of responsiveness or sensitivity
Elasticity analysis helps answer questions such as:
Can Microsoft increase revenue if it increases the price of any of its software products?
How do oil prices change if OPEC restricts output?
How large a tax is needed to discourage a substantial number of people from smoking?
If Congress passes a law forcing firms to provide health care, how effectively can firms pass on the full amount of these mandatory fees to consumers?
If a proposed tax on sugar-sweetened beverages occurs, what are the implications concerning sales for those beverages?

17. Elasticity (con’t.)
Elasticity: the percentage change in y due to a unit percentage change in x:
change from (x1,y1) into (x2, y2)
Point elasticity y y1 y2 x1 x2 x

18. Demand Elasticity Own-price elasticity Cross-price elasticity
Income elasticity
Other elasticity concepts

19. Own-Price Elasticity of Demand
Own-Price Elasticity of Demand: summarizes the sensitivity of the quantity demanded response due to own-price changes.
Interpretation: 1% increase (decrease) in the product price leads to an ε% decrease (increase) in quantity demanded.

20. Own Price Elasticity (Con’t.)
Price Elasticity Formula:
The product price changes from p1 to p2, and the quantity changes from Q1 to Q2 correspondingly.
Point Elasticity:

21. Own-Price Elasticity: Examples
Linear demand: Q = a-b*P
Constant elasticity demand: Q = a*p-b
Why is the own-price elasticity negative?

22. Types of Own-Price Elasticity
Elastic: the % change in quantity demanded is greater than the % change in price.
Inelastic: the % change in quantity demanded is less than the % change in price.
Unitary: the % changes in quantity demanded and price are the same.
Special cases:
Perfectly elastic
Perfectly inelastic

23. Perfectly Inelastic Demand Curve: εp = 0
Price per unit ($)

24. Perfectly Elastic Demand Curve: εp = ∞

25. Price Elasticity of Demand Varies Along Linear Demand Curve
Figure 4.10

26. Price Elasticity and Revenue Maximization
Revenue: R = p*Q, Marginal revenue MR:
The change in revenue if the price goes down:
Linear demand case: P = a-b*Q
Price elasticity:
Marginal revenue: MR = a-2*b*Q
Total revenue is maximized where MR = 0
Elastic demand ↑
Inelastic demand ↓
Unitary demand
No change

27. Own-Price Elasticity, Marginal Revenue, and Revenue Maximization

28. Own-Price Elasticity and Optimal Pricing
Optimal pricing (in what sense?): MR=MC
Assumption: a firm can affect market price (under what conditions?)
Optimal price:

29. Cross-price Elasticity
What-if Question: If the price of product x changes, how much does the quantity demanded of product y change?
Interpretation: Measures how responsive demand is to changes in prices of other goods, holding everything else constant.
Examples

30. Cross Price Elasticity (cont’)
Formula:
Point elasticity:
Examples

31. Demand Curve for Lipton Tea
PLipton Tea
Rightward demand shift due to a rise in the price of Nestea D1 D0
QLipton Tea
Suppose the price of Nestea rises, all other factors invariant?

32. Demand Curve for Lipton Tea
PLipton Tea
Leftward demand shift due to a rise in the price of hamburgers D0 D1
QLipton Tea
Suppose the price of hamburgers rises, all other factors invariant?

33. Cross-Price Elasticity (Con’t.)
Substitutes vs Complements
Two goods are Substitutes if a price increase (decrease) in one good leads to an increase (decrease) in quantity demanded of the other good. Examples: butter and margarine; cotton and polyester; beef, pork, and chicken.
Two goods are Complements if a price increase (decrease) in one good leads to a decrease (increase) in quantity demanded of the other good. Examples: chips and salsa; computers and software; shoes and socks.

34. Income Elasticity
Income Elasticity: a measure of responsiveness of the quantity demanded to income.
Point elasticity:

35. Suppose the income of consumers rises, all other factors invariant?
PLipton Tea
Rightward shift in the demand curve for Lipton Tea due to a rise in income D1 D0
QLipton Tea
Suppose the income of consumers rises, all other factors invariant?

36. As drawn, what kind of good is Lipton Tea?
Income IB IA QA QB
QLipton Tea
As drawn, what kind of good is Lipton Tea?

37. Income Elasticity (Con’t.)
Necessary goods: products for which demand is positively related to income; EI>0 and EI<1. (Engel curve is positively sloped)
Luxury goods: products for which demand is positively related to income; EI > 1. (Engel curve is positively sloped)
Normal goods: either necessary goods or luxury goods
Inferior goods: products for which consumer demand declines as income rises; EI<0. (Engel curve is negatively sloped)

38. Summary: Demand, Supply, and Market Equilibrium Elasticity:
Own-price elasticity
Cross-price elasticity (shift in the demand curve)
Income elasticity (shift in the demand curve)
Engel curve