经济学双语

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Marginal utility

Marginal utility is the additional utility gained from consuming an additional unit of a good. 增加一单位的产品消费时所得到的效 用的增量.
Pints/yr 200 Marginal utility of chocolate ice cream (utils/ pint) 16 Pints/yr 100
Translating Wants into Demand

Marginal utility vanilla/P

$12/1 = 12 utils/$ 16/2 = 8 utils/$
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250 Pints/yr
Marginal Utility Curves for Two Flavors of Ice Cream (III)
Marginal utility of chocolate ice cream
MU Chocolate 20 Price Chocolate 2
(utils/ pint) 20

Economic Naturalist Needs vs. Wants • Why does California experience chronic (长期的）water shortages? The price of water is too low. Need – basic necessities– food clothing and shelter. Want– desire
(utils/ pint)
12 8
200 Pints/yr
300
Marginal Utility Curves for Two Flavors of Ice Cream (II)
Marginal utility of chocolate ice cream
24 (utils/ pint)
Sarah decreases chocolate spending by $100, and MUC/PC = 24/$2 = 12 > MUV/pV = 8
Cost
Is ―Free Ice Cream‖ really free? The demand curve is a relationship between the quantity demanded and all costs– monetary and non-monetary – associated with acquiring a goods. 需求曲线是需求量与获取该产品所付出的所有 成本—货币的和非货币的--之间的关系.
Diminishing Marginal Utility
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Utils/cone
Sarah’s marginal utility
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Translating Wants into Demand

The Law of Diminishing Marginal Utility (边际效用递减规律)
The Law of Demand
The benefit of an activity equals the highest price we’d be willing to pay to pursue it (i.e., the reservation price). As the cost of an activity rises and exceeds the reservation price, less of the activity will be pursued.


Sarah should buy more vanilla
Marginal Utility Curves for Two Flavors of Ice Cream (II)
Marginal utility of vanilla ice cream
Sarah increases vanilla spending by $100, and MUV/PV = 8/$1 = 8
本章提出效用最大化的概念,并研究需求曲线背后的消费 者选择模型.它展示了理性支出原则,并解释价格变化的 替代效应和收入效应对需求的影响.
The Law of Demand (需求定理)

People do less of what they want to do as the cost of doing it rises. 当做某件事情的成本上升时,人们将会选 择降低做此事的频率.

The tendency for the additional utility gained from consuming an additional unit of a good to diminish as consumption increases beyond some point. 随着消费数量的增加,从每增加消费的一 单位产品中所获得的效用是递减的.
Translating Wants into Demand

Question

Is Sarah maximizing her total utility?
Marginal utility of vanilla ice cream (utils/ pint)
12
Marginal Utility Curves for Two Flavors of Ice Cream (I)

This chapter develops the idea of utility maximization and the model of consumer choice behind the demand curve. It presents the Rational Spending Rule and explains how changes in the price of substitutes and income affect demand.
Translating Wants into Demand

How should we allocate our incomes among the various goods and services that are available? 应该怎样将我们的收入分配到各种各 样的产品和服务上呢?
Translating Wants into Demand

Allocating A Fixed Income Between Two Goods

Assume
• Two goods: Chocolate and vanilla ice cream • Price of chocolate equals $2/pint • Price of vanilla equals $1/pint • Sarah’s budget = $400/yr • Currently Sarah is consuming 200 pints of vanilla and 100 pints of chocolate
75 Pints/yr
Translating Wants into Demand

Assumption • People allocate their income to maximize their satisfaction or total utility. 假设:人们总是试图调整其收入在各种 物品和服务中的分配以实现满足程 度的最大化.

The Law of Demand

The Origins of Demand What determines ―tastes‖ or ―preferences‖? • Biology 生理 • Culture 文化 • Peer Influences 同等人群的影响
The Law of Demand
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Chapter Five
Demand: The Benefit Side of The Market
Main contents of the chapter
Sarah’s Total Utility from Ice Cream Consumption
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Utils/hour
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Translating Wants Into Demand
What should Sarah do when she gets to the front of the line? What do you think?
utility maximization效用最大化
Translating Wants into Demand

Measuring Wants: The Concept of Utility Utility • The satisfaction people derive from their consumption activities. • 人们从自己的消费行为中得到的满足程度.
Sarah’s Total Utility from Ice Cream Consumption
Cone quantity (cones/hour) 0 1 2 3 4 5 6 Total utility (utils/hour) 0 50 90 120 140 150 140
How much ice cream should Sarah consume if the ice cream is ―free‖?
16
50
Pints/yr
100
Marginal Utility Curves for Two Flavors of Ice Cream (III)
Marginal utility of vanilla ice cream
(utils/ pint)
MU Vanilla 10 Price Vanilla 1


Is the time spent in the line relevant to how many cones to order?
Sarah’s Total Utility and Marginal Utility from Ice Cream Consumption
Cone quantity (cones/hour) Total utility (utils/hour) Marginal utility (utils/cone)
The Law of Diminishing Marginal Utility

Reasons:
Biology 生理 psychology 心理 properties: subjective vary according to time and conditions
《最好吃的东西》
免子和猫争论，世界上什么东西最好吃。免子 说，“世界上萝卜最好吃。萝卜又甜又脆又解渴， 我一想起萝卜就要流口水。”猫不同意，说， “世界上最好吃的东西是老鼠。老鼠的肉非常嫩， 嚼起来又酥又松，味道美极了！”免子和猫争论 不休、相持不下，跑去请猴子评理。猴子听了， 不由得大笑起来：“瞧你们这两个傻瓜蛋，连这 点儿常识都不懂！世界上最好吃的东西是什么？ 是桃子！桃子不但美味可口，而且长得漂亮。我 每天做梦都梦见吃桃子。”免子和猫听了，全都 直摇头。那么，世界上到底什么东西最好吃？

Marginal utility chocolate/P

Translating Wants into Demand
If Sarah spends $2 less on chocolate, utilities will decline by 16. If Sarah spends $2 more on vanilla, utilities will increase by 24 So…