限界効用と個人需要曲線
導入済み| English | 意味 |
|---|---|
| marginal utility/ˈmɑːdʒɪnl juːˈtɪlɪti/ | 限界効用 |
| diminishing marginal utility/dɪˈmɪnɪʃɪŋ ˈmɑːdʒɪnl juːˈtɪlɪti/ | 限界効用逓減の法則 |
A decision you can investigate
- The first bottle of water after exercise is highly valued; a fifth bottle may add little satisfaction.
- The benefit of one more unit differs from total satisfaction from all units.
Build the explanation
- Marginal utility 边际效用 is additional satisfaction from an extra unit. Diminishing marginal utility 边际效用递减 means each further unit adds less satisfaction over the relevant range. With other factors fixed, a lower price may be needed to make additional units worth buying; this helps explain downward individual demand.
- Demand requires willingness and ability to buy at alternative prices. Own price changes give movements along demand. Substitute/complement prices, real income, tastes, population size/age and advertising can shift demand.
Work through the evidence
- A fictional buyer with enough budget has maximum willingness to pay for four bottles of 12, 8, 5 and 2 yuan. At price 6, the first two are worth buying but the third is not: quantity is 2, with total payment 12. At price 4, quantity becomes 3.
- If safe drinking fountains become more available, demand for purchased water may shift left because a substitute is more attractive. A hot-weather preference change may shift it right; these shifts differ from the movement after water’s own price changes.
価格6において、この消費者はボトルをいくつ選ぶか？
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第三のボトルの評価額は 5 であり、価格を下回っている。
限界効用が正でありながら減少している場合、総効用に何が起こり得るか？
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各単位が依然として満足感をもたらすが、その量は減る。
限界効用が減少することは、追加される単位数ごとに総満足度が低下することを意味する。
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正の増加分が減少しても、総満足度は引き続き上昇し続けることがある。
Test the limits
- The example uses willingness-to-pay units as a monetary representation of marginal valuation, not direct measurement of psychological utility. Diminishing marginal utility does not mean total utility must fall; it can rise more slowly.
- The individual model does not by itself determine market demand: aggregate buyers differ. A simultaneous income or substitute-price change can invalidate an own-price-only interpretation.
より直接的に需要シフトを引き起こすのは何か？
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代替財の変化は、各価格における評価額を変化させる。
Apply and explain your answer
- Why does quantity rise from 2 to 3 when price falls from 6 to 4?
- The third bottle’s marginal valuation of 5 now exceeds its price.
用語とそれぞれの意味を結びつけよ。
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各用語を、その明示された経済的関係に用いること。
Use the terms precisely
- marginal utility: Additional satisfaction from consuming one more unit.
- diminishing marginal utility: Additional satisfaction falls as more units are consumed over a stated range.
A fictional buyer with enough budget has maximum willingness to pay for four bottles of 12, 8, 5 and 2 yuan. At price 6, the first two are worth buying but the third is not: quantity is 2, with total payment 12. At price 4, quantity becomes 3. If safe drinking fountains become more available, demand for purchased water may shift left because a substitute is more attractive. A hot-weather preference change may shift it right; these shifts differ from the movement after water’s own price changes.
The example uses willingness-to-pay units as a monetary representation of marginal valuation, not direct measurement of psychological utility. Diminishing marginal utility does not mean total utility must fall; it can rise more slowly. The individual model does not by itself determine market demand: aggregate buyers differ. A simultaneous income or substitute-price change can invalidate an own-price-only interpretation.
Marginal utility is additional satisfaction from an extra unit. Diminishing marginal utility means each further unit adds less satisfaction over the relevant range. With other factors fixed, a lower price may be needed to make additional units worth buying; this helps explain downward individual demand.