By summarising the content of each powerpoint slide we provide the outline of a lesson plan. By clicking on the blue numbers, you can reproduce any individual slide, or even use it as a diagram or summary of the formulae of price and income elasticity to handout in class.

1. Elasticity

2. Elasticity elasticity quantifies the response in one variable when another variable changes. Price elasticity: %  change in demand with respect to % change in price.

3. Price Elasticity of Demand Slope and Elasticity Slope Is Not a Useful Measure of Responsiveness Changing the unit of measure from pounds to ounces changes the numerical value of the demand slope dramatically, but the behaviour of buyers in the two diagrams is identical.

4. Price Elasticity of Demand Slope and Elasticity price elasticity of demand The ratio of the percentage of change in quantity demanded to the percentage of change in price; measures the responsiveness of quantity demanded to changes in price.

5. Price Elasticity of Demand Types of Elasticity perfectly inelastic demand Demand in which quantity demanded does not respond at all to a change in price. Demand Elasticities for Four Products – 1. Insulin +10% 0% = 0 (Perfectly inelastic) 2. Basic telephone service +10% -1%  = -.1 (Inelastic) 3. Beef +10% -10% = -1.0 (Unitarily elastic) 4. Bananas +10% -30% = -3.0 (Elastic.)

6. Price Elasticity of Demand Types of Elasticity Perfectly Inelastic and Perfectly Elastic Demand Curves Figure (a) shows a perfectly inelastic demand curve for insulin. Price elasticity of demand is zero. Quantity demanded is fixed; it does not change at all when price changes. nFigure (b) shows a perfectly elastic demand curve facing a wheat farmer. A tiny price increase drives the quantity demanded to zero. Perfectly elastic demand implies that individual producers can sell all they want at the going market price but cannot charge a higher price.

7. Price Elasticity of Demand Types of Elasticity inelastic demand Demand that responds somewhat, but not a great deal, to changes in price. Inelastic demand always has a numerical value between 0 and -1. A warning: You must be very careful about signs. Because it is generally understood that demand elasticities are negative (demand curves have a negative slope), they are often reported and discussed without the negative sign.

8. Price Elasticity of Demand Types of Elasticity unitary elasticity A demand relationship in which the percentage change in quantity of a product demanded is the same as the percentage change in price in absolute value (a demand elasticity of -1). elastic demand A demand relationship in which the percentage change in quantity demanded is larger than the percentage change in price in absolute value (a demand elasticity with an absolute value greater than 1). perfectly elastic demand Demand in which quantity drops to zero at the slightest increase in price.

9. Price Elasticity of Demand Types of Elasticity A good visual way to remember the difference between the two “perfect” elasticities is: E and I (see slide).

10. Calculating Elasticities Calculating Percentage Changes To calculate percentage change in quantity demanded using the initial value as the base, the following formula is used: see slide.

11. Calculating Elasticities Calculating Percentage Changes We can calculate the percentage change in price in a similar way. Once again, let us use the initial value of P—that is, P1—as the base for calculating the percentage. By using P1 as the base, the formula for calculating the percentage of change in P is: see slide.

12. Calculating Elasticities Elasticity Is a Ratio of Percentages Once all the changes in quantity demanded and price have been converted to percentages, calculating elasticity is a matter of simple division. Recall the formal definition of elasticity: % change in quantity demanded / % change in price

13. Calculating Elasticities Elasticity Changes Along a Straight-Line Demand Curve Demand Curve for Lunch at the Office Dining Room Between points A and B, demand is quite elastic at – 6.4. Between points C and D, demand is quite inelastic at -.294. Demand Schedule for Office Dining Room Lunches Price (£ per Lunch)

14. Calculating Elasticities Elasticity and Total Revenue In any market, P x Q is total revenue (TR) received by producers (the same as total spending by consumers): When price (P) declines, quantity demanded (QD) increases. The two factors, P and QD move in opposite directions: TR = P x Q total revenue = price x quantity

15. Calculating Elasticities Elasticity and Total Revenue Because total revenue is the product of P and Q, whether TR rises or falls in response to a price increase depends on which is bigger: the percentage increase in price or the percentage decrease in quantity demanded. If the percentage decline in quantity demanded following a price increase is larger than the percentage increase in price, total revenue will fall.

16. Calculating Elasticities Elasticity and Total Revenue The opposite is true for a price cut. When demand is elastic, a cut in price increases total revenues: When demand is inelastic, a cut in price reduces total revenues: effect of price cut on a product with elastic demand.

17. The Determinants of Demand Elasticity Availability of Substitutes The greater the availability of substitutes, the higher the elasticity value. The Importance of Being Unimportant When an item represents a relatively small part of our total budget, we tend to pay little attention to its price. The value is less elastic. The Time Dimension The elasticity of demand in the short run may be very different from the elasticity of demand in the long run. In the longer run, demand is likely to become more elastic, or responsive, simply because households make adjustments over time and producers develop substitute goods.

18. The Determinants of Demand Elasticity Elasticities at a Delicatessen in the Short Run and Long Run The graph shows the expected relationship between long-run and short-run demand for Frank’s sandwiches. Notice if you raise prices above the current level, the expected quantity change read off the short-run curve is less than that from the long-run curve.

19. Other Important Elasticities Income Elasticity of Demand income elasticity of demand A measure of the responsiveness of demand to changes in income.

20. Other Important Elasticities Cross-Price Elasticity Of Demand cross-price elasticity of demand A measure of the response of the quantity of one good demanded to a change in the price of another good.

21. Other Important Elasticities Elasticity Of Supply elasticity of supply A measure of the response of quantity of a good supplied to a change in price of that good. Likely to be positive in output markets.

22. Key Terms • cross-price elasticity of demand • elastic demand • elasticity • elasticity of supply • income elasticity of demand • inelastic demand • midpoint formula • perfectly elastic demand • perfectly inelastic demand • price elasticity of demand • unitary elasticity

23. Appendix Point Elasticity (Optional) Point Elasticity Changes Along a Demand Curve