• The price elasticity of supply is computed as the percentage change in the quantity supplied divided by the percentage change in price.
需要の変化率（％）
• 需要の弾力性＝ ー－－－－－－－－－
価格の変化率（％）
Price elasticity of supply =
Percentage change in quantity supplied
Percentage change in price
THREE APPLICATIONS OF SUPPLY, DEMAND,
AND ELASTICITY 供給、需要および弾力性の応用
• Can good news for farming be bad news for farmers?
よい収穫は農家に対して悪いのか。
• What happens to wheat farmers and the market for wheat when university agronomists discover a new wheat when university agronomists discover a new wheat hybrid that is more productive than existing varieties?
大学の農学者はより生産的小麦の雑種を開
発した場合は、小麦農家に何かの変化が引
き起こるのか。
Can Good News for Farming Be Bad News for Farmers?
よい収穫は農家に対して悪いのか
• Examine whether the supply or demand curve shifts.
供給曲線と需要曲線の変化を検証しよう。
• Determine the direction of the shift of the curve.
それは各曲線の方向を決めるのだ。
• Use the supply-and-demand diagram to see how the market equilibrium changes.
供給表と需要表を利用してその変化を見てみ
よう
。Figure 7 An Increase in Supply in the Market for Wheat 小麦市場において生産量の増加：小麦価格の下落
Price of Wheat
S1
S2 2. . . . leads
to a large fall in price . . .
1. When demand is inelastic, an increase in supply . . .
$3
Quantity of Wheat 0
3. . . . and a proportionately smaller increase in quantity sold. As a result,
Demand 2
110 100
Compute the Price Elasticity of Demand When There Is a Change in Supply
供給の変化により需要の価格弾力性を計算してみよ
ED
100 110 100 110 2
3 00 2 00 3 00 2 00 2
( ) /
. .
( . . ) /
0 095
0 4. 0 24
. .
Demand is inelastic.
需要は非弾力的
Why Did OPEC Fail to Keep the Price of Oil High?
なぜ石油輸出機構は石油価格の向上を維持できないのか
• Supply and Demand can behave differently in the short run
and the long run 供給と需要の短期的反応と長期的反応
は異なる。
• In the short run, both supply and demand for oil are
relatively inelastic 短期的に石油の供給と需要は非弾力
的であるが、
的であるが、
• But in the long run, both are elastic 長期的に両方とも弾 力的である。
• Production outside of OPEC OPEC以外の国の石油生産
• More conservation by consumers 消費者の石油在庫の 増加
• その他の要因：例えば、エコカー、省エネ製品の開発
Does Drug Interdiction Increase or Decrease Drug-Related Crime?
麻薬禁止法は麻薬からみ犯罪を減少できるか
• Drug interdiction impacts sellers rather than buyers.
麻薬禁止は買いてより売り手を制限する
• Demand is unchanged. Equilibrium price rises although quantity falls.
麻薬の需要は変わらない。そして、麻薬量の減少 麻薬の需要は変わらない。そして、麻薬量の減少
にも関わらず均衡価格が上昇。
• Drug education impacts the buyers rather than sellers.
麻薬使用の教育は買い手より売り手に効果がある
• Demand is shifted. Equilibrium price and quantity are lowered.
需要はシフトしたら、均衡価格と量は低下。
Price of Drugs Price of Drugs
Drug Interdiction 麻薬禁止 Drug Education 麻薬使用の教育
S2
S1 S1
It is amazing how
Figure 9 Policies to Reduce the Use of Illegal Drugs 不法麻薬使用減少の政策効果
Quantity of Drugs Quantity of Drugs
D2
D1 D1
The demand for illegal drugs is inelastic.
Interdiction shifts the supply,
while education shifts the demand.
In each case, the change in price is the same. But in one market the price goes up.
The changes in quantities (and TR) are
It is amazing how useful knowledge of elasticities can be!