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Chapter 7 Elasticity of Demand and Supply. Demand Elasticity (Price Elasticity of Demand). E d = (%∆Q d )/(%∆P) = { (Q d2 - Q d1 )/[(Q d1 + Q d2 )/2]}/ {(P 2 – P 1 )/[(P 1 + P 2 )/2]} E d represented as positive by convention, though actually always negative
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Demand Elasticity(Price Elasticity of Demand) • Ed = (%∆Qd)/(%∆P) = {(Qd2 - Qd1)/[(Qd1 + Qd2)/2]}/ {(P2 – P1)/[(P1 + P2)/2]} • Ed represented as positive by convention, though actually always negative • due to downward-sloping demand curve • hence always take absolute value
Determinants of Price Elasticity of Demand Demand tends to be more elastic or less inelastic: • if the good is a luxury; • the longer the time period; • the greater the number of close substitutes; and • the more narrowly defined the market.
Determinants of Price Elasticity of Demand Demand tends to be more inelastic or less elastic: • if the good is a necessity; • the shorter the adjustment time; • if there are few good substitutes; and • the more broadly defined the market.
Chapter 20 Figure 20.2(b) Total Revenue and Elasticity
ComputingDemand Elasticity Demand for Ice Cream ED = (8 - 10) / 9 2.20 ($2.20 - $2.00) / $2.10 2.00 8 10
Computing Demand Elasticity Demand for Ice Cream ED = (22%) 2.20 (9.5%) 2.00 8 10
Computing Demand Elasticity Demand for Ice Cream ED 2.32 = 2.20 2.00 8 10
Computing Demand Elasticity Demand for Ice Cream Demand is Elastic ED 2.32 = 2.20 2.00 8 10
Supply Elasticity(Price Elasticity of Supply) • Es = (%∆Qs)/(%∆P) = {(Qs2 - Qs1)/[(Qs1 + Qs2)/2]}/ {(P2 – P1)/[(P1 + P2)/2]} • Es always positive • due to upward-sloping demand curve • hence never take absolute value
Cross Elasticities(Cross-Price Elasticity of Demand) • Exy = (%∆Qdx)/(%∆Py) • = {(Qdx2 - Qdx1)/[(Qdx1 + Qdx2)/2]}/ {(Py2 – Py1)/[(Py1 + Py2)/2]} • Exy measures responsiveness of the demand for x to changes in the price of y • Positive for substitutes • Negative for complements • never take absolute value
Income Elasticities(Income Elasticity of Demand) • Ei = (%∆Qd)/(%∆Y) = {(Qd2 - Qd1)/[(Qd1 + Qd2)/2]}/ {(Y2 – Y1)/[(Y1 + Y2)/2]} • Ei measures responsiveness of demand for x to changes in (average) consumer income • Positive for normal goods • Negative for inferior goods • never take absolute value