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Elasticity What is it and how to calculate it? The Concept of Elasticity • Elasticity is a measure of the responsiveness of one variable to another. • The greater the elasticity, the greater the responsiveness. Laugher Curve Q. What’s the difference between an economist and a befuddled old man with Alzheimer’s? A. The economist is the one with a calculator. The Concept of Elasticity • Elasticity is a measure of the responsiveness of one variable to another. • The greater the elasticity, the greater the responsiveness. Price Elasticity • The price elasticity of demand is the percentage change in quantity demanded divided by the percentage change in price. Percentage change in quantity demanded ED = Percentage change in price Price Elasticity • The price elasticity of supply is the proportional change in quantity demanded relative to the proportional change in price. Percentage change in quantity supplied ES = Percentage change in price What Information Price Elasticity Provides • Price elasticity of demand and supply gives the exact quantity response to a change in price. Classifying Demand and Supply as Elastic or Inelastic • Demand or supply is elastic if the percentage change in quantity is greater than the percentage change in price. E>1 Classifying Demand and Supply as Elastic or Inelastic • Demand or supply is inelastic if the percentage change in quantity is less than the percentage change in price. E<1 Elastic Demand and Supply • Elastic supply means that quantity changes by a greater percentage than the percentage change in price. • The same holds true for demand. Inelastic Demand and Supply • Inelastic supply means that quantity doesn't change much with a change in price. • The same holds true for demand. Elasticity Is Independent of Units • Percentages allow us to have a measure of responsiveness that is independent of units. • This makes comparisons of responsiveness of different goods easier. Calculating Elasticities • To determine elasticity divide the percentage change in quantity by the percentage change in price. The End-Point Problem • The end-point problem – the percentage change differs depending on whether you view the change as a rise or a decline in price. The End-Point Problem • Economists use the average of the end points to calculate the percentage change. (Q2 - Q1) Elasticity = (P 2 - P1) ½Q2 Q1 ½P1 + P2 Graphs of Elasticities B $26 24 22 20 18 16 14 0 C (midpoint) A D Elasticity of demand between A and B = 1.27 10 12 14 Quantity of software (in hundred thousands) Graphs of Elasticities $6.00 5.50 5.00 4.50 4.00 3.50 3.00 0 A B C (midpoint) Elasticity of supply between A and B = 0.18 470 480 490 Quantity of workers Calculating Elasticity Q 2 Q1 1 %Q 2 (Q1 Q 2 ) E P2 P1 %P 1 ( P P ) 1 2 2 Calculating Elasticity of Demand Between Two Points $26 24 22 20 18 16 Elasticity of demand between A and B: B midpoint C A % Q E % P 10 14 4 1 .33 2 (14 10) ED 12 1.27 26 20 6 .26 1 23 2 (26 20) Demand 14 0 10 12 14 Quantity of software (in hundred thousands) Calculating Elasticity of Supply Between Two Points $6.00 5.50 5.00 4.50 4.00 3.50 3.00 0 A C Elasticity of supply between A and B: E %Q B % P 485 475 10 1 .021 480 2 ( 485 475) ES .2 5 4.50 .50 .105 1 4.75 2 (5 4.50) 470 480 490 Quantity of workers Calculating Elasticity at a Point • Let us now turn to a method of calculating the elasticity at a specific point, rather than over a range or an arc. Calculating Elasticity at a Point • To calculate elasticity at a point, determine a range around that point and calculate the arc elasticity. Calculating Elasticity at a Point $10 9 8 7 6 5 4 3 2 1 (28 - 20) E at A = C ½28 20 0.66 (5 - 3) ½5 + 3 A B 20 24 28 40 Quantity Calculating Elasticity at a Point $10 9 8 7 6 5 4 3 2 1 To calculate elasticity at a point determine a range around that point and calculate the arc elasticity. C Eat A A B 20 24 28 Quantity 28 20 8 1 .33 2 (28 20) 24 .66 53 2 .5 1 4 2 (5 3) 40 Elasticity and Supply and Demand Curves • Two important points to consider: – Elasticity is related (but is not the same as) slope. – Elasticity changes along straight-line demand and supply curves. Calculating Elasticity at a Point $10 9 8 7 6 5 4 3 2 1 Demand A Supply EA = 2.33 D C E = 0.75 C 6 ED = 0.86 EB = 0.11 B 12 18 24 30 36 42 48 54 60 Quantity Elasticity and Supply and Demand Curves • Two important points to consider: – Elasticity is related (but is not the same as) slope. – Elasticity changes along straight-line demand and supply curves. Elasticity Is Not the Same as Slope • The steeper the curve at a given point, the less elastic is supply or demand. • There are two limiting examples of this. Elasticity Is Not the Same as Slope • When the curves are flat, we call the curves perfectly elastic. • The quantity changes enormously in response to a proportional change in price (E = ). Elasticity Is Not the Same as Slope • When the curves are vertical, we call the curves perfectly inelastic. • The quantity does not change at all in response to an enormous proportional change in price (E = 0). Perfectly Inelastic Demand Curve Perfectly inelastic demand curve 0 Quantity Perfectly Elastic Demand Curve Perfectly elastic demand curve 0 Quantity Elasticity Changes Along Straight-Line Curves • Elasticity is not the same as slope. • Elasticity changes along straight line supply and demand curves–slope does not. Elasticity Along a Demand Curve Ed = ∞ $10 9 8 7 6 5 4 3 2 1 Elasticity declines along demand curve as we move toward the quantity axis Price Ed > 1 0 Ed = 1 Ed < 1 Ed = 0 1 2 3 4 5 6 7 8 9 10 Quantity Elasticity Along a Supply Curve S0 Price $10 9 8 7 6 5 4 3 2 1 0 S1 Es declines Es = Es rises Es = 0 1 2 3 4 5 6 Quantity 7 If the supply curve intersects the vertical axis, Es declines as you go up the supply curve. If the supply curve intersects the quantity axis, Es increases as you go up the supply curve.