1. Price, Income and Cross Elasticity

2. Elasticity – the concept
The responsiveness of one variable to changes in another
When price rises, what happens to demand?
Demand falls
BUT!
How much does demand fall?

3. Elasticity – the concept
If price rises by 10% - what happens to demand?
We know demand will fall
By more than 10%?
By less than 10%?
Elasticity measures the extent to which demand will change

4. Elasticity 4 basic types used: Price elasticity of demand
Price elasticity of supply
Income elasticity of demand
Cross elasticity

5. Elasticity Price Elasticity of Demand
The responsiveness of demand to changes in price
Where % change in demand is greater than % change in price – elastic
Where % change in demand is less than % change in price - inelastic

6. Elasticity The Formula: % Change in Quantity Demanded
___________________________
Ped =
% Change in Price
If answer is between 0 and -1: the relationship is inelastic
If the answer is between -1 and infinity: the relationship is elastic
Note: PED has – sign in front of it; because as price rises
demand falls and vice-versa (inverse relationship between
price and demand)

7. Elasticity Price (£) Quantity Demanded
The demand curve can be a range of shapes each of which is associated with a different relationship between price and the quantity demanded.
Quantity Demanded

8. Elasticity Total Revenue Price £5 D 100 Quantity Demanded (000s)
Total revenue is price x quantity sold. In this example, TR = £5 x 100,000 = £500,000.
This value is represented by the grey shaded rectangle.
The importance of elasticity is the information it provides on the effect on total revenue of changes in price. £5
Total Revenue D
100
Quantity Demanded (000s)

9. Elasticity D Total Revenue Price £5 £3 100 140
If the firm decides to decrease price to (say) £3, the degree of price elasticity of the demand curve would determine the extent of the increase in demand and the change therefore in total revenue. £5 £3
Total Revenue D
100
140
Quantity Demanded (000s)

10. Elasticity % Δ Price = -50% % Δ Quantity Demanded = +20%
Producer decides to lower price to attract sales 10
% Δ Price = -50%
% Δ Quantity Demanded = +20%
Ped = -0.4 (Inelastic)
Total Revenue would fall 5
Not a good move! D 5 6
Quantity Demanded

11. Elasticity Producer decides to reduce price to increase sales
% Δ in Price = - 30%
% Δ in Demand = + 300%
Ped = - 10 (Elastic)
Total Revenue rises 10
Good Move! 7 D 5 20
Quantity Demanded

12. Elasticity If demand is price elastic:
Increasing price would reduce TR (%Δ Qd > % Δ P)
Reducing price would increase TR
(%Δ Qd > % Δ P)
If demand is price inelastic:
Increasing price would increase TR
(%Δ Qd < % Δ P)
Reducing price would reduce TR (%Δ Qd < % Δ P)

14. Price Elasticity of Demand
Definition:
Law of demand tells us that consumers will respond to a price drop by buying more, but it does not tell us how much more. The degree of sensitivity of consumers to a change in price is measured by the concept of price elasticity of demand.
Price elasticity formula: Ed = percentage change in Qd / percentage change in Price.
If the percentage change is not given in a problem, it can be computed using the following formula:
Percentage change in Qd = (Q1-Q2) / [1/2 (Q1+Q2)] where Q1 = initial Qd, and Q2 =  new Qd.
Percentage change in P = (P1-P2) / [1/2 (P1 + P2)] where P1 = initial Price, and P2 = New Price.
Putting the two above equations together:
Ed = {(Q1-Q2) / [1/2 (Q1+Q2)] } / {(P1-P2) / [1/2 (P1 + P2)]}
Because of the inverse relationship between Qd and Price, the Ed coefficient will always be a negative number. But, we focus on the magnitude of the change by neglecting the minus sign and use absolute value
Examples:
1.  If the price of Product A  increased by 10%,  the quantity demanded decreased by 20%. Then the coefficient for  price elasticity of the demand of Product A is:
Ed = percentage change in Qd / percentage change in Price = (20%) / (10%) = 2
2. If the quantity demanded of Product B has decreased from 1000 units to 900 units as price increased from $2 to $4 per unit, the coefficient for Ed is:
Ed = {(Q1-Q2) / [1/2 (Q1+Q2)] } / {(P1-P2) / [1/2 (P1 + P2)]} = {( ) / 1/2( )} / {(2 - 4) / 1/2 (2+4)} =
Take the absolute value of , Ed = 0.16

15. Elasticity Income Elasticity of Demand:
The responsiveness of demand to changes in incomes
Normal Good – demand rises as income rises and vice versa
Inferior Good – demand falls as income rises and vice versa

16. Elasticity Income Elasticity of Demand:
A positive sign denotes a normal good
A negative sign denotes an inferior good

17. Income Elasticity of Demand
Definition:
Income elasticity of demand (Ey, here y stands for income) tells us the relationship a product's quantity demanded and income. It measures the sensitivity of quantity demand change of product X to a change in income.
Price elasticity formula: Ey = percentage change in Quantity demanded / percentage change in Income
If the percentage change is not given in a problem, it can be computed using the following formula:
Percentage change in Qx = (Q1-Q2) / [1/2 (Q1+Q2)] where Q1 = initial Qd, and Q2 =  new Qd.
Percentage change in Y = (Y1-Y2) / [1/2 (Y1 + Y2)] where Y1 = initial Income, and Y2 = New income.
Putting the two above equations together:
Ey = {(Q1-Q2) / [1/2 (Q1+Q2)] } / (Y1-Y2) / [1/2 (Y1 + Y2)]
Characteristics:
Ey > 1,  Qd and income are directly related. This is a normal good and it is income elastic.
0< Ey<1,  Qd and income are directly related. This is a normal good and it is income inelastic.
Ey < 0, Qd and income are inversely related. This is an inferior good.
Ey approaches 0, Qd   stays the same as income changes, indicating a necessity.
Example:
If income  increased by 10%,  the quantity demanded of a product increases by 5 %. Then the coefficient for the income  elasticity of demand for this product is::
Ey = percentage change in Qx / percentage change in Y = (5%) / (10%) = 0.5 > 0, indicating this is a normal good and it is income inelastic.

18. Elasticity For example:
Yed = - 0.6: Good is an inferior good but inelastic – a rise in income of 3% would lead to demand falling by 1.8%
Yed = + 0.4: Good is a normal good but inelastic – a rise in incomes of 3% would lead to demand rising by 1.2%
Yed = + 1.6: Good is a normal good and elastic – a rise in incomes of 3% would lead to demand rising by 4.8%
Yed = - 2.1: Good is an inferior good and elastic – a rise in incomes of 3% would lead to a fall in demand of 6.3%
This slide has a ten second gap in between each example to allow the teacher to explain how the figures have been calculated. This gap can be increased or reduced as appropriate using the custom animation tool.

19. Elasticity Cross Elasticity:
The responsiveness of demand of one good to changes in the price of a related good – either a substitute or a complement
% Δ Qd of good t
__________________
Xed =
% Δ Price of good y

20. Elasticity Goods which are complements: Goods which are substitutes:
Cross Elasticity will have negative sign (inverse relationship between the two)
Goods which are substitutes:
Cross Elasticity will have a positive sign (positive relationship between the two)

21. Cross Elasticity of Demand
Definition:
Cross elasticity (Exy) tells us the relationship between two products. it measures the sensitivity of quantity demand change of product X to a change in the price of product Y.
Formula: Exy = percentage change in Quantity demanded of X / percentage change in Price of Y.
If the percentage change is not given in a problem, it can be computed using the following formula:
Percentage change in Qx = (Q1-Q2) / [1/2 (Q1+Q2)] where Q1 = initial Qd of X, and Q2 =  new Qd of X.
Percentage change in Py = (P1-P2) / [1/2 (P1 + P2)] where P1 = initial Price of Y, and P2 = New Price of Y.
Putting the two above equations together:
Exy = {(Q1-Q2) / [1/2 (Q1+Q2)] } / {(P1-P2) / [1/2 (P1 + P2)]}
Characteristics:
Exy > 0,  Qd of X and Price of Y are directly related. X and Y are substitutes.
Exy approaches 0, Qd of X  stays the same as the Price of Y changes. X and Y are not related.
Exy < 0, Qd of X and Price of Y are inversely related. X and Y are complements.
Examples:
1. If the price of Product A  increased by 10%,  the quantity demanded of B increases by 15 %. Then the coefficient for the cross  elasticity of the A and B is :
Exy = percentage change in Qx / percentage change in Py = (15%) / (10%) = 1.5 > 0, indicating A and B are substitutes.
2. If the price of Product A  increased by 10%,  the quantity demanded of B decreases by 15 %. Then the coefficient for the cross  elasticity of the A and B is :
Exy = percentage change in Qx / percentage change in Py = (- 15%) / (10%) = < 0, indicating A and B are complements.

22. Elasticity Price Elasticity of Supply:
The responsiveness of supply to changes in price
If Pes is inelastic - it will be difficult for suppliers to react swiftly to changes in price
If Pes is elastic – supply can react quickly to changes in price
% Δ Quantity Supplied
____________________
Pes =
% Δ Price

24. Price Elasticity of Supply
Definition:
Law of supply tells us that producers will respond to a price drop by producing less, but it does not tell us how much less. The degree of sensitivity of producers to a change in price is measured by the concept of price elasticity of supply.
Price elasticity formula: Es = percentage change in Qs / percentage change in Price.
If the percentage change is not given in a problem, it can be computed using the following formula:
Percentage change in Qs = (Q1-Q2) / [1/2 (Q1+Q2)] where Q1 = initial Qs, and Q2 =  new Qs.
Percentage change in P = (P1-P2) / [1/2 (P1 + P2)] where P1 = initial Price, and P2 = New Price.
Putting the two above equations together:
Es = {(Q1-Q2) / [1/2 (Q1+Q2)] } / {(P1-P2) / [1/2 (P1 + P2)]}
Because of the direct relationship between Qs and Price, the Es coefficient will always be a positive number.
Examples:
1.  If the price of Product A  increased by 10%,  the quantity supplied increases by 5%. Then the coefficient for  price elasticity of the supply of Product A is:
Es = percentage change in Qs / percentage change in Price = (5%) / (10%) = 0.5
2. If the quantity supplied of Product B has decreased from 1000 units to 200 units as price decreases from $4 to $2 per unit, the coefficient for Es is:
Es = {(Q1-Q2) / [1/2 (Q1+Q2)] } / {(P1-P2) / [1/2 (P1 + P2)]} = {( ) / 1/2( )} / {(4-2) / 1/2 (4+2)} = 2

25. Characteristics & Determinants
Es approaches infinity, supply is perfectly elastic. Producers are very sensitive to price change.
Es > 1, supply is elastic. Producers are relatively responsive to price changes.
Es = 1, supply is unit elastic. Producers’ response and price change are in same proportion.
Es < 1, supply is inelastic. Producers are relatively unresponsive to price changes.
Es approaches 0, supply is perfectly inelastic. Producers are very insensitive to price change.
It is impossible to judge elasticity of a supply curve by its flatness or steepness. Along a linear supply curve, its elasticity changes.
Determinants:
1. Time lag: How soon the cost of increasing production rises and the time elapsed since the price change influence the Es. The more rapidly the production cost rises and the less time elapses since a price change, the more inelastic the supply. The longer the time elapses, more adjustments can be made to the production process, the more elastic the supply.
2. Storage possibilities: Products that cannot be stored will have a less elastic supply. For example, produces usually have inelastic supply due to the limited shelf life of the vegetables and fruits.

26. Determinants of Elasticity
Time period – the longer the time under consideration the more elastic a good is likely to be
Number and closeness of substitutes – the greater the number of substitutes, the more elastic
The proportion of income taken up by the product – the smaller the proportion the more inelastic
Luxury or Necessity - for example, addictive drugs

27. Importance of Elasticity
Relationship between changes in price and total revenue
Importance in determining what goods to tax (tax revenue)
Importance in analysing time lags in production
Influences the behaviour of a firm
This slide also has an automatic response with ten second gaps in between each point. At this stage we have tried to keep things as simple as possible but to introduce issues that will be dealt with later in the course.