Basic Economic Concepts
AP Microeconomics Topic 1 8:34 English narration · English + 中文 subtitles burned in
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Transcript
A day has only twenty-four hours.
一天只有二十四小时。
Think what you want to fit into one: sleep, school, homework, sport, time with friends.
想想你希望塞进一天里的事：睡觉、上学、写作业、运动， 还有和朋友相处的时间。
Add it up honestly and it comes to about thirty.
老实算一算，大约需要三十小时。
The wants keep growing. The hours never do.
欲望不断增长，时间却从不增加。
That gap is called scarcity, and it is where economics begins.
这个缺口叫做稀缺性，经济学正是由此开始。
Every hour you spend costs the hour you did not spend elsewhere.
你花掉的每一小时都有代价——那就是你没有用在别处的这一小时。
Today we build the foundation of microeconomics.
今天我们来打好微观经济学的基础。
Scarcity and the three questions.
稀缺性与三个基本问题。
Opportunity cost.
机会成本。
The production possibilities curve.
生产可能性曲线。
Comparative advantage and the gains from trade.
比较优势与贸易利得。
And marginal thinking — the habit that runs through the whole course.
还有边际思维—— 贯穿整门课程的思考习惯。
Let's begin.
让我们开始吧。
Everything an economy produces comes out of four resources, and we call them the factors of production.
一个经济体生产的一切，都来自四种资源，我们称之为生产要素。
Land is the natural resources.
土地是自然资源。
Labor is human effort.
劳动是人的付出。
Capital is the tools, machines and buildings we produce with.
资本是我们用来生产的工具、机器和厂房。
Entrepreneurship organises the other three and takes the risk.
企业家才能则把前三者组织起来并承担风险。
All four are limited.
这四者都是有限的。
So every society must answer the same three questions. What to produce? How to produce it?
因此每个社会都必须回答同样的三个问题。
And for whom?
生产什么？
The way it answers them is its economic system.
怎样生产？ 为谁生产？
Because you cannot have everything, you must choose.
既然不能什么都要，你就必须选择。
Opportunity cost is the value of the next best alternative you give up.
机会成本是你放弃的次优选择的价值。
Picture your Saturday, with four things you could do.
设想你的星期六有四件可做的事。
You choose the concert, the one you wanted most.
你选了去听音乐会，那是你最想做的。
The next best was playing in the match — so that match is your opportunity cost.
次优的选择是去打那场比赛——所以那场比赛就是你的机会成本。
Now notice what it is not.
现在注意它不是什么。
It is not the second, the third and the fourth added together.
它不是第二、第三和第四加在一起。
Only the next best one counts.
只有次优的那一个才算。
And it is not the ticket price — it is the game you missed.
它也不是门票的钱，而是你错过的那场比赛。
So who answers those questions?
那么究竟由谁来回答这些问题？
In a market economy, private buyers and sellers decide, and prices coordinate them — Adam Smith's invisible hand.
在市场经济中，私人买者和卖者做决定， 由价格来协调他们。
In a command economy, the government owns the resources and a plan sets what gets made.
亚当·斯密称之为"看不见的手"。
Incomes are more equal, but incentives are weak and shortages common.
在计划经济中，政府拥有资源，由中央计划决定生产什么。
Almost every real country is a mixed economy: mostly markets, with government supplying some goods.
收入更平均， 但激励不足、短缺常见。
Here is the strength of markets.
几乎每个真实国家都是混合经济：以市场为主， 政府提供一部分物品，并纠正市场做不好的地方。
Prices carry information and incentives at once.
市场的强大之处正在于此： 价格同时传递信息和激励，而且不需要中央计划者。
Economists draw all of this in one picture: the production possibilities curve, the P P C.
经济学家用一张图画出这一切：生产可能性曲线。
Imagine a country that makes only two goods.
设想一个国家只生产两种物品。
The curve shows every largest combination it can produce when its resources are fully used.
这条曲线表示当资源和技术被充分利用时， 它能生产的所有最大组合。
Watch a point move along it. To get more of one good, the country must give up some of the other.
看一个点沿着曲线移动： 要多得到一种物品，这个国家就必须放弃一些另一种物品。
That trade-off is opportunity cost, in a picture.
这种取舍就是机会成本，被画成了一条线。
Three positions matter, and the exam asks about all three.
有三个位置很重要，考试三个都会问。
A point on the curve uses every resource fully, so it is efficient.
曲线上的点把每一份资源都用足了， 所以是有效率的。
A point inside the curve wastes resources — idle machines, workers with no job.
曲线内部的点浪费了资源——闲置的机器、没有工作的工人。
A point outside the curve is unattainable today: there are not enough resources.
曲线外部的点今天无法实现，因为资源根本不够。
And here is the skill that earns marks. The slope of the curve is the opportunity cost.
接下来是能拿分的技能：曲线的斜率就是机会成本。
Step to the right, and the drop is what you gave up.
沿着曲线向右迈一步，你看到的下降量正是你所放弃的。
Why is the curve usually drawn bowed outwards?
为什么这条曲线通常画成向外凸出？
Take equal steps to the right along it, and watch the drops.
沿着它向右迈出相等的步子，看那些下降量。
The first is small.
第一次下降很小。
The next is bigger.
第二次更大。
The third is bigger still.
第三次更大。
That is increasing opportunity cost.
这就是机会成本递增。
The reason is simple: resources are not equally good at both jobs.
原因很简单：资源并非同样擅长两种工作。
You move the least suited ones first, so little is lost.
你先调走最不适合的那些， 所以损失很少。
Keep going and you must move resources that were excellent at the old job.
继续下去，你就不得不调走原本非常擅长旧工作的资源， 于是每一步的代价都更高。
A straight line would say the opposite — that opportunity cost never changes.
而直线所说的完全不同——机会成本从不改变。
Now move the whole curve.
现在让整条曲线移动。
Find more resources, invent better technology, or train a larger workforce, and the entire curve shifts outward.
找到更多资源、发明更好的技术，或者培养更多劳动力， 整条曲线就向外移动。
That is economic growth: more of both goods becomes possible.
这就是经济增长：两种物品都能生产得更多。
War or disaster does the opposite and pushes the curve inward.
战争或自然灾害则相反，把曲线推向内侧。
One choice matters most here. Capital goods are the tools and machines that make other goods; consumer goods are used directly.
这里有一个选择比其他都重要： 资本品是用来生产其他物品的工具和机器，而消费品被人们直接使用。
Build more capital goods today, and your curve sits further out tomorrow.
今天多造资本品，明天你的曲线就位于更外面。
Now two producers.
现在来看两个生产者。
In a day, Anna can make twenty shirts, or ten tables.
一天之内，安娜能做二十件衬衫，或者十张桌子。
Ben can make twelve shirts, or twelve tables.
本能做十二件衬衫，或者十二张桌子。
Anna has the absolute advantage in shirts: she simply makes more.
安娜在衬衫上有绝对优势，因为她做得更多。
But that is not what matters.
但重要的并不是绝对优势。
Work out the opportunity cost of one table instead.
我们改算一张桌子的机会成本。
For Anna, one table costs two shirts.
对安娜来说，一张桌子要付出两件衬衫。
For Ben, one table costs one shirt.
对本来说，一张桌子只要一件衬衫。
Ben has the lower opportunity cost, so Ben specializes in tables and Anna in shirts.
本的机会成本更低，所以本应当做桌子，安娜应当做衬衫。
Comparative advantage decides who specializes, and specializing is what creates the gain.
决定谁来专业化的是比较优势，而不是绝对优势。
Now they trade, and the rate they settle on is the terms of trade.
现在他们进行交易，双方定下的比率叫做贸易条件。
Both sides gain when the rate sits between the two opportunity costs — between one shirt per table and two.
当这个比率处在两个机会成本之间时，双方都获益—— 也就是在每张桌子一件衬衫和两件衬衫之间。
Say they agree on one and a half shirts for a table.
假设他们商定一张桌子换一件半衬衫。
Ben gains, because a table cost him one shirt and he now receives one and a half.
本获益，因为一张桌子只花了他一件衬衫，而他现在得到一件半。
Anna gains too, because a table would have cost her two shirts and she pays only one and a half.
安娜也获益，因为一张桌子本来要花她两件衬衫，而她现在只付一件半。
Together they produce more, so both can consume outside their own curve.
合起来他们生产的比各自单干时更多，所以双方都能消费到自己曲线之外。
Every decision comes down to weighing benefit against cost.
每个决策归根到底都是在权衡收益与成本。
Do it only if the benefit is at least as big as the cost — and the cost includes the opportunity cost, not just the money. Now a classic trap.
只有当收益至少和成本一样大时才去做—— 而且要记住，成本包括机会成本，不只是花掉的钱。
You paid fifty dollars for a match ticket.
下面是一个经典陷阱。
Match day comes and it is pouring with rain.
你花五十美元买了一张比赛门票。
Should the fifty dollars make you go? No. That money is gone either way.
比赛当天大雨倾盆，你其实更想待在温暖的家里。
Compare only what is still ahead.
那五十美元该让你非去不可吗？ 不。
Money already spent that you cannot get back is a sunk cost.
那笔钱无论如何都已经没了。 只比较还在前面的东西。
It is ignored — always ignore sunk costs, because they are the same whichever way you choose.
已经花掉且收不回来的钱叫沉没成本，而沉没成本永远不属于任何决策。
Most real choices are not all or nothing. They are a little more, or a little less.
大多数真实的选择不是"全有或全无"，而是"多一点，或者少一点"。
So we use marginal analysis, comparing at the margin.
所以我们在边际上作比较。
Marginal benefit is the extra benefit from one more unit, and it usually falls as quantity rises.
边际收益是多生产或多消费一单位所带来的额外收益， 它通常随数量上升而下降。
Marginal cost is the extra cost of one more unit, and it usually rises.
边际成本是多一单位的额外成本，它通常上升。
While marginal benefit sits above marginal cost, keep going, because each extra unit is still worth it.
只要边际收益高于边际成本，就继续下去，因为每多一单位仍然值得。
Once marginal cost climbs higher, you have gone too far.
一旦边际成本超过边际收益，你就走过头了。
So the best quantity is exactly where they are equal.
所以最佳数量正好在两者相等之处，那一点带来最大的净收益。
Where does that falling marginal benefit come from?
边际收益为什么会下降？ 来自我们自己。
From us. The first slice of pizza is wonderful.
第一片披萨美味无比。
The second is good.
第二片不错。
By the fifth you barely want it.
到第五片你几乎不想吃了。
Each extra unit gives less extra satisfaction — the law of diminishing marginal utility. Out of it comes the rule for spending a budget.
每多一单位带来的额外满足更少， 经济学家称之为边际效用递减法则。
That gives the utility-maximizing rule: spend so that the marginal utility per dollar is the same for every good, and use the whole budget up.
由此得出花预算的规则： 让每一元钱带来的边际效用在所有物品上都相同，并且把预算全部花完。
If one good gives more satisfaction per dollar, buy more of it, until the two match.
如果某种物品每一元带来的满足更多，就多买它—— 而当你这样做时，它的边际效用会下降，直到两者相等。
Let's use that rule.
我们来用一下这条规则。
Good X gives twenty utils of satisfaction and costs two dollars.
物品X带来二十单位效用，价格是两美元。
Good Y gives fifteen utils and costs one dollar.
物品Y带来十五单位效用，价格是一美元。
Which should the consumer buy more of?
消费者应该多买哪一种？
Pause here and try it.
先暂停，自己试一试。
Ready?
好了吗？
For good X, twenty divided by two is ten utils per dollar.
对物品X，二十除以二等于每美元十单位效用。
For good Y, fifteen divided by one is fifteen utils per dollar.
对物品Y，十五除以一等于每美元十五单位效用。
Y gives more satisfaction for every dollar spent, so buy more Y and less X.
Y在每一美元上带来的满足更多，所以消费者应当多买Y、少买X。
As you do, Y's marginal utility falls and X's rises, until the two match.
随着这样做，Y的边际效用下降、X的边际效用上升， 直到两个比值相等，预算也刚好花完。
Before you go, three marks students give away.
结束之前，三个学生白白丢掉的分。
First, opportunity cost is the next best alternative only — never the total of everything you gave up.
第一，机会成本只是次优的那一个选择—— 绝不是你放弃的一切之和。
Second, a sunk cost is money already spent, so leave it out of the decision completely.
第二，沉没成本是已经花掉的钱， 所以要把它完全排除在决策之外。
Third, comparative advantage is about the lower opportunity cost, not about producing more.
第三，比较优势看的是更低的机会成本， 而不是产量更多。
Get those three right, and this unit is yours.
把这三点做对，这个单元就是你的了。