文档介绍：Chapter 3 Elasticity Theory
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The contents of the chapter
is elasticity?
2. Elasticity of Demand
3. Elasticity of Supply
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is elasticity?
弹性elasticity:
自变量变动一个百分比所引起的因变量变动的百分比。(注意:不是因变量变动量与自变量变动量之比。)
e= ( Δ Y/Y)/( Δ X/X)=(ΔY/ ΔX)•( X/Y )
弹性是一个具体的数值coefficient,与变量之间的度量无关。
为什么用弹性:
通过弹性,可以表示存在函数关系的变量与变量之间反应的敏感程度并做出量化分析,从而能更好地认识变量之间的相互关系。
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Elasticity is a measure of responsiveness. Two words are important here. The word "measure" means that elasticity results are reported as numbers, or elasticity coefficients. The word "responsiveness" means that there is a stimulus-reaction involved. Some change or stimulus causes people to react by changing their behavior, and elasticity measures the extent to which people react.
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2. Elasticity of Demand
Qd=f( P, I, Pi,Pe…)
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Price elasticity of demand
The mon elasticity measurement is that of price elasticity of demand. It measures how much consumers respond in their buying decisions to a change in price.
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弹性公式Elasticity formula
弧弹性公式arc elasticity formula:
ΔQ Pa
Ed=- ——•——(a点到b点的弹性)
ΔP Qa
ΔQ Pb
Ed=- ——•——(b点到a点的弹性)
ΔP Qb
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弧弹性公式(中点公式)
ΔQ/(Qa+Qb)/2 ΔQ Pa+Pb
Ed = -————————或=- —× ——
ΔP/(Pa+Pb)/2 ΔP Qa+Qb
点弹性公式与计算
dQ/Q dQ P
Ed =- ——或= -—×—
dP/P dP Q
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