Choice, models and market adjustment
Pearson Edexcel · International A-Level · Economics Topic 1 6:48 English narration · English + 中文 subtitles burned in
Chapters
Transcript
One model runs through this topic.
本主题只用一个模型。
Demand is quantity equals 140 minus 2 P; supply is quantity equals 20 plus 4 P.
需求为数量等于 140 减 2P；供给为数量等于 20 加 4P。
They meet at a price of 20 and a quantity of 100.
两者在价格 20、数量 100 处相交。
Elasticities, surplus and tax incidence all come from these two lines.
弹性、剩余和税负归宿都来自这两条线。
Economics cannot run laboratory experiments on whole economies, so it builds models, holding all else equal.
经济学无法对整个经济做实验室实验，所以它建立模型，并假设其他条件不变。
A positive statement can be tested against evidence: the tax raised 3 billion pounds.
实证表述可以用证据检验：这项税收入了 30 亿英镑。
A normative statement adds a value judgement: the tax is too high.
规范表述加入价值判断：这项税太高了。
Scarcity is unlimited wants against finite resources.
稀缺是无限的欲望面对有限的资源。
So we must choose, and the real cost of any choice is its opportunity cost: the benefit of the next-best alternative forgone.
所以我们必须选择，而任何选择的真正代价是它的机会成本：放弃的次优选择的收益。
The frontier shows maximum productive potential.
生产可能性边界显示最大生产潜力。
A point ON the frontier is efficient.
边界上的点是有效率的。
A point inside wastes resources.
边界内的点浪费资源。
A point outside is unobtainable today.
边界外的点今天无法达到。
The frontier bows outward, because resources are not equally suited to all uses.
边界向外凸出，因为资源并不同样适合所有用途。
More or better resources, or new technology, shift it outward.
更多或更好的资源、新技术会使它向外移动。
The division of labour raises output per worker, but work becomes repetitive.
劳动分工提高人均产出，但工作变得重复。
Specialists must exchange, and money makes that work: as a medium of exchange, a measure of value, a store of value, and a method of deferred payment.
专业化的人必须交换，货币让交换成为可能：它是交换媒介、价值尺度、价值储藏和延期支付手段。
In a free market, prices allocate resources without a planner, but inequality and market failure follow.
在自由市场中，价格在没有计划者的情况下配置资源，但会带来不平等和市场失灵。
In a command economy the state allocates directly, but it misreads preferences and weakens incentives.
在计划经济中，国家直接配置资源，但会误判偏好并削弱激励。
A mixed economy combines the two.
混合经济把两者结合起来。
The model assumes consumers maximise utility and firms maximise profit.
模型假设消费者追求效用最大化，企业追求利润最大化。
Real people depart from it: herding, habit and inertia, poor computational skills, the need to feel valued, and framing or bias.
现实中的人会偏离：从众、习惯和惰性、计算能力差、渴望被重视，以及框架效应或偏见。
A change in the good's own price is a movement ALONG the demand curve.
商品自身价格的变化是沿着需求曲线的移动。
A change in any other determinant, such as income or the price of a substitute, SHIFTS the whole curve.
其他任何决定因素的变化，例如收入或替代品价格，都会使整条曲线移动。
Each extra item gives less additional satisfaction than the last.
每多一件商品带来的额外满足都比前一件少。
For example, the first drink adds 10 units of utility, the second 7, the third 4.
例如，第一杯饮料带来 10 单位效用，第二杯 7，第三杯 4。
Because each extra unit is worth less, you only buy another at a lower price: so the demand curve slopes downward.
因为每多一件价值更低，你只有在价格更低时才会再买：所以需求曲线向下倾斜。
On the shared model, raise the price from 20 to 22: plus 10 percent.
在同一模型上，把价格从 20 提高到 22：上升百分之 10。
Quantity demanded falls from 100 to 96: minus 4 percent.
需求量从 100 降到 96：下降百分之 4。
PED is minus 4 over 10: minus 0.4, price inelastic.
PED 等于负 4 除以 10，即负 0.4，缺乏价格弹性。
Total revenue rises from 2000 to 22 times 96, which is 2112.
总收入从 2000 升到 22 乘 96，即 2112。
Along a straight-line demand curve, PED is not constant.
沿着一条直线需求曲线，PED 并不是常数。
It is elastic at high prices, unitary at the midpoint, and inelastic at low prices.
高价时富有弹性，中点处为单位弹性，低价时缺乏弹性。
At a price of 20 we are in the inelastic part.
价格为 20 时处于缺乏弹性的部分。
Total revenue peaks at the midpoint: a price of 35 and a quantity of 70, giving 2450.
总收入在中点达到最大：价格 35、数量 70，等于 2450。
Income elasticity: income up 10 percent raising quantity 8 percent gives plus 0.8, a normal good that is income inelastic.
收入弹性：收入上升百分之 10，数量上升百分之 8，得正 0.8，是缺乏收入弹性的正常品。
A negative YED marks an inferior good.
YED 为负说明是劣等品。
Cross elasticity: good X up 10 percent raising the quantity of Y by 10 percent gives plus 1.0, close substitutes.
交叉弹性：X 的价格上升百分之 10，Y 的数量上升百分之 10，得正 1.0，是相近的替代品。
A negative XED marks complements.
XED 为负说明是互补品。
On the shared supply curve, raise the price from 20 to 24: plus 20 percent.
在同一条供给曲线上，把价格从 20 提高到 24：上升百分之 20。
Quantity supplied rises from 100 to 116: plus 16 percent.
供给量从 100 升到 116：上升百分之 16。
PES is 16 over 20: plus 0.8, so supply is inelastic.
PES 等于 16 除以 20，即正 0.8，所以供给缺乏弹性。
Supply is more elastic in the long run, when all factors can change.
长期中所有要素都可以调整，供给更有弹性。
It is also more elastic with stocks that keep, mobile factors of production, and spare capacity.
有可储存的库存、生产要素流动性强、有闲置产能时，供给也更有弹性。
Legal limits make it less elastic.
法律限制则使它更缺乏弹性。
At 25, sellers offer 120 but buyers want 90: an excess supply of 30 pushes the price down.
价格为 25 时，卖方供应 120，买方只要 90：超额供给 30 迫使价格下降。
At 15, buyers want 110 but sellers offer 80: an excess demand of 30 pushes it up.
价格为 15 时，买方要 110，卖方只供应 80：超额需求 30 推动价格上升。
market forces move both back to 20.
市场力量把两者都推回 20。
Consumer surplus is the triangle under demand and above the price: one half times 100 times 70 minus 20, which is 2500.
消费者剩余是需求曲线以下、价格以上的三角形：二分之一乘 100 乘（70 减 20），等于 2500。
Producer surplus lies below the price and above supply: a rectangle of 20 times 20, plus a triangle of one half times 80 times 20: 400 plus 800, 1200.
生产者剩余在价格以下、供给曲线以上：20 乘 20 的矩形，加上二分之一乘 80 乘 20 的三角形：400 加 800，等于 1200。
The price mechanism has three functions.
价格机制有三个功能。
Rationing: a higher price rations a scarcer good.
配给：更高的价格对更稀缺的商品进行配给。
Incentive: it rewards producers of that good.
激励：它奖励该商品的生产者。
Signalling: the change tells everyone where resources are valued.
信号：价格变化告诉所有人资源在哪里更受重视。
A unit tax of 6 shifts supply up by 6.
每单位 6 的税使供给曲线上移 6。
The new equilibrium: consumers pay 24 at a quantity of 92, and producers keep 18.
新均衡：消费者在数量 92 处支付 24，生产者保留 18。
Government revenue is 6 times 92: 552.
政府收入为 6 乘 92，即 552。
With the tax, supply becomes 4 P minus 4.
征税后，供给变为 4P 减 4。
Setting 140 minus 2 P equal to it gives a price of 24 and a quantity of 92.
令 140 减 2P 等于它，得到价格 24、数量 92。
Consumers pay 4 more; producers receive 2 less.
消费者多付 4，生产者少收 2。
Demand is more inelastic than supply, so consumers bear the larger share.
需求比供给更缺乏弹性，所以消费者承担更大份额。
A subsidy of 6 shifts supply down: 4 P plus 44.
每单位 6 的补贴使供给下移：4P 加 44。
Setting 140 minus 2 P equal to it gives a price of 16 and an output of 108.
令 140 减 2P 等于它，得到价格 16、产量 108。
Producers receive 22.
生产者得到 22。
Consumers gain 4, producers gain 2, and taxpayers pay 6 times 108: 648.
消费者得益 4，生产者得益 2，纳税人支付 6 乘 108，即 648。
Check yourself.
自我检测。
A price rise from 20 to 22 gives a PED of minus 0.4, inelastic.
价格从 20 升到 22，PED 为负 0.4，缺乏弹性。
Total revenue peaks at 35 and 70: 2450.
总收入在 35 和 70 处达到最大：2450。
Consumer surplus at 20 is 2500.
价格为 20 时消费者剩余为 2500。
A tax of 6 raises the consumer price to 24 and revenue to 552.
6 的税使消费者价格升到 24，收入 552。
And a YED below zero marks an inferior good.
YED 小于零说明是劣等品。