The price system and the microeconomy (A Level)
A-Level Economics Topic 7 18:50 English narration · English + 中文 subtitles burned in
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Transcript
Look at these shoppers.
看看这些购物的人。
Each has a limited budget, and every extra thing they buy gives a little less pleasure than the last.
每个人的预算都有限，而他们每多买一件东西， 带来的快乐都比上一件少一点。
Now a huge steel plant: it makes steel far more cheaply than a small workshop.
再看一座巨大的钢铁厂：它生产钢材比小作坊便宜得多。
One idea explains both — always ask what one more unit adds.
有一个想法可以解释这两件事——永远要问，多一个单位带来了什么。
Economists call that satisfaction utility.
经济学家把这种满足感叫做效用。
Total utility is the satisfaction from everything you consume.
总效用是你消费的全部所带来的满足。
Marginal utility is the extra satisfaction from one more unit.
边际效用是多消费一个单位所带来的额外满足。
Marginal utility falls: each extra unit adds less than the one before.
边际效用在下降：每多一个单位带来的满足都比上一个少。
That is diminishing marginal utility.
这就是边际效用递减。
Total utility still rises, but it flattens.
总效用仍在上升，但越来越平缓。
How should a shopper spend a budget?
一位消费者应该如何花掉固定的预算？
Think of a balance.
把它想成一架天平。
Total utility is greatest when the last dollar on each good gives the same extra utility — the equi-marginal principle.
当花在每种商品上的最后一元带来的额外效用相同时，总效用最大——这就是等边际原则。
If one good gives more per dollar, buy more until the sides match.
如果某种商品每元带来的效用更多，就多买一些，直到两边相等。
Because marginal utility falls, you only buy more at a lower price: that is why demand slopes downward.
因为边际效用递减，你只有在价格更低时才会多买，这就是需求向下倾斜的原因。
Know its limitations, though: utility cannot really be measured in numbers, people do not calculate like this, and it ignores habit and advertising.
但效用本身其实无法被真正衡量。
Another way to draw the same choice.
还有第二种方式来表示同一个选择。
The budget line shows every bundle the shopper can just afford.
预算线画出消费者刚好买得起的所有组合。
An indifference curve joins bundles that give the same total utility.
无差异曲线把带来相同总效用的组合连起来。
A higher curve means more utility, but this one is unaffordable.
更高的曲线代表更多效用，但这一条买不起。
The best they can reach is where the budget line touches the highest curve — that tangency is consumer equilibrium.
他们能达到的最好结果，是预算线与最高曲线相切之处——这个切点就是消费者均衡。
Before we move on, be ready to criticise this model, because examiners ask for it.
在往下讲之前，要能对这个模型提出批评，因为考官会问到。
First, utility cannot really be measured in numbers — there is no unit of satisfaction, so the neat equations rest on something you cannot observe.
第一，效用其实无法用数字度量——满意度没有单位， 所以那些整齐的方程建立在你无法观测的东西之上。
Second, nobody actually calculates like this at the supermarket; people use habit and rules of thumb.
第二，在超市里没有人真的这样计算；人们靠的是习惯和经验法则。
Third, it ignores habit, addiction and advertising, which plainly do shift what people buy.
第三，它忽略了习惯、成瘾和广告，而这些显然会改变人们的购买。
It is still worth knowing, because it gives the clearest reason WHY demand curves slope down.
它仍然值得掌握，因为它给出了需求曲线为什么向下倾斜的最清晰理由。
Now let one price fall.
现在让一种商品的价格下降。
The shopper buys more, for two reasons.
消费者会买得更多，原因有两个。
The substitution effect: the good is cheaper than others, so they switch towards it.
替代效应：这种商品比其他商品便宜了，于是他们转向它。
The income effect: the same money buys more, so real income has risen.
收入效应：同样的钱能买到更多，实际收入上升了。
For a normal good both effects agree.
对于正常品，两种效应方向一致。
For an inferior good the income effect works backwards, but is weaker.
对于低档品，收入效应方向相反，但更弱。
A Giffen good is the rare case where it wins: demand falls.
吉芬品则是收入效应占上风的罕见情况：需求反而下降。
Now sort goods by how those two effects combine.
现在按这两种效应如何叠加来给商品分类。
For a normal good, both effects push the same way: cheaper, so you switch towards it, and richer, so you buy more of it.
对正常品，两种效应方向一致： 变便宜了，所以你转向它；变富了，所以你买得更多。
For an inferior good the income effect works the OTHER way — feeling richer makes you buy less of it — but that effect is usually the weaker one, so demand still rises when the price falls.
对低档品，收入效应方向相反——觉得更富了反而少买它—— 但这种效应通常较弱，所以价格下降时需求仍然上升。
A Giffen good is the rare case where the income effect is so strong it wins outright, so demand FALLS when the price falls.
吉芬品是罕见的情形：收入效应强到完全占了上风， 于是价格下降时需求反而下降。
Its demand curve slopes upward, which is the only exception you will meet.
它的需求曲线向上倾斜，这是你会遇到的唯一例外。
Now judge how well a market works.
现在来判断一个市场运作得好不好。
Productive efficiency means lowest cost.
生产效率指以最低成本生产。
Allocative efficiency means making what people most want, where price equals marginal cost.
配置效率指生产人们最想要的东西，此时价格等于边际成本。
Pareto optimality means nobody gains without someone losing.
帕累托最优指没有人能在不使别人变差的情况下变好。
Dynamic efficiency means improving over time.
动态效率指随时间不断改进。
Miss these and you get market failure: monopoly power, externalities, public goods, information failure, factor immobility.
做不到这些，就出现市场失灵——垄断势力、外部性、公共物品、信息失灵、要素不流动性。
Here is the biggest cause.
这是市场失灵最大的原因。
The firm's own cost curve is marginal private cost.
企业自己的成本曲线是边际私人成本。
Add the cost pollution puts on everyone else — a negative externality — and you get marginal social cost.
把污染加在其他人身上的成本加进去，就得到边际社会成本。
The market produces where private cost meets demand, so it makes too much.
市场在私人成本与需求相交处生产，因此产量过多。
Society's best output is lower, and the triangle between them is welfare nobody gets — the deadweight welfare loss.
社会最优产量更低，两者之间的三角形就是没有人得到的福利——无谓损失。
Externalities work both ways.
外部性在两个方向上都起作用。
Private cost plus external cost is social cost.
私人成本加外部成本就是社会成本。
On the other side, private benefit plus external benefit is social benefit.
另一边，私人收益加外部收益就是社会收益。
Society's best output is where marginal social cost equals marginal social benefit.
社会最优产量在边际社会成本等于边际社会收益之处。
The market stops where the private curves cross.
而市场却停在两条私人曲线相交的地方。
So a negative externality like pollution gives too much, and a positive externality like education gives too little.
所以污染带来生产过多，教育带来生产过少。
Both are market failure, and both invite the government.
两者都是市场失灵，也都是政府介入的原因。
Five cost words, and questions mix them deliberately.
有五个成本词，而考题会故意把它们混在一起。
Fixed cost does not change with output — the rent on the factory is the same whether you make one unit or a thousand.
固定成本不随产量变化——不管你造一件还是一千件，厂房租金都一样。
Variable cost changes with output, like raw materials.
可变成本随产量变化，比如原材料。
Total cost is the two added together.
总成本是这两者相加。
Average cost is total cost per unit, T C over Q.
平均成本是每单位的总成本，也就是 T C 除以 Q。
And marginal cost is the cost of ONE more unit, the change in total cost over the change in quantity.
而边际成本是再多生产一件的成本， 是总成本的变化量除以数量的变化量。
Notice the last two are different questions: average asks what each unit costs on average, marginal asks what the NEXT one costs.
注意后两个问的是不同的问题：平均问的是每一件平均花多少， 边际问的是下一件要花多少。
Now the firm's costs.
现在来看企业的成本。
The vertical axis is cost per unit.
纵轴是单位成本。
Average variable cost is variable cost per unit.
平均可变成本是每单位的可变成本。
Average cost is total cost per unit, so the gap between them is fixed cost per unit.
平均成本是每单位的总成本，所以两条曲线之间的差距就是每单位的固定成本。
Marginal cost is the cost of one more unit: in the short run it falls, then rises, from diminishing returns. All of this is marginal analysis — decide by the next unit, never the average.
边际成本是多生产一个单位的成本：它先下降后上升，原因是边际报酬递减。
And here is the mark students miss — marginal cost cuts both average curves at the lowest point.
下面是学生最常丢的分——边际成本从两条平均曲线的最低点穿过。
Use those definitions.
用一用这些定义。
Ten units cost five hundred pounds in total; eleven cost five hundred and forty.
生产十个单位的总成本是五百英镑，生产十一个单位是五百四十英镑。
Pause here and try it yourself.
先暂停，自己算一算。
Average cost is total cost divided by quantity: five hundred over ten, so fifty pounds.
平均成本等于总成本除以数量：五百除以十，等于五十英镑。
Marginal cost is the change in total cost over the change in quantity, so forty pounds.
边际成本等于总成本的变化除以数量的变化，等于四十英镑。
That is below average cost, so the eleventh unit pulls the average down.
这低于平均成本，所以第十一个单位把平均成本拉了下来。
That rule never fails.
这条规律从不例外。
One more.
再来一道。
A firm makes one hundred units at twelve pounds each, with an average cost of nine.
一家企业生产一百个单位，每个卖十二英镑，平均成本是九英镑。
Supernormal profit is average revenue minus average cost, times quantity — three hundred pounds.
超常利润等于平均收益减平均成本，再乘以数量——三百英镑。
Average revenue sits above average cost, so it is supernormal.
平均收益高于平均成本，所以它是超常利润。
Here is a rule that earns marks on every cost diagram, and it is just arithmetic about averages.
下面这条规则在每一张成本图上都能拿分，而它不过是关于平均数的算术。
In the worked example the marginal cost of forty was BELOW the average of fifty, and making that unit pulled the average DOWN.
在刚才的例题里，边际成本四十低于平均成本五十， 多做那一件就把平均值拉低了。
That is general: a marginal value below the average always pulls the average down, and a marginal value above it pushes the average up.
这是普遍成立的： 边际值低于平均值，总是把平均值往下拉； 边际值高于平均值，就把平均值往上推。
So the average can only stop falling and start rising at the exact point where marginal crosses it — which is why MC cuts AC at AC's minimum, every time.
所以平均值只能在边际值恰好穿过它的那一点由降转升—— 这正是 M C 每一次都在 A C 的最低点穿过它的原因。
And why does MC rise at all?
那么 M C 又为什么会上升呢？
Diminishing returns: adding more workers to a fixed number of machines, each extra worker eventually adds less output, so each extra unit costs more.
因为边际报酬递减： 在机器数量固定的情况下不断加人，每多一个工人最终增加的产出越来越少， 于是每多一件产品的成本就越来越高。
In the long run every factor can change, so we look at returns to scale, and the long-run average cost curve is U-shaped.
在长期，每一种要素都可以改变，所以我们看规模报酬， 而长期平均成本曲线是 U 形的。
Going down the left side are economies of scale: buying in bulk, using big specialised machines, and letting workers specialise.
沿着左半边向下是规模经济： 批量采购、使用大型专用机器、以及让工人专业化分工。
That is the steel plant from the opening — it makes steel far more cheaply than a workshop could.
这就是开头那座钢厂——它炼钢比一个作坊便宜得多。
But keep growing past the minimum and average cost RISES again: diseconomies of scale, caused by poor communication and the sheer difficulty of controlling a huge organisation.
但如果越过最低点继续扩张，平均成本又会上升：这是规模不经济， 由沟通不畅以及管理一个庞大组织本身的困难所造成。
The lowest point of the curve is the most efficient size for that industry.
曲线的最低点就是该行业最有效率的规模。
In the long run every factor can change, so we look at returns to scale.
在长期，所有要素都可以改变，所以我们看规模报酬。
As output rises the same fixed overheads spread over more units, so cost per unit falls.
产量上升时，同样的固定管理费用被分摊到更多单位上，于是单位成本下降。
Those are economies of scale: bulk buying, bigger machines, specialised staff.
这就是规模经济：批量采购、更大的机器、专门化的员工。
Grow too big and control gets harder — average cost turns and rises.
但长得太大，管理就更难——平均成本转头上升。
That is diseconomies of scale.
这就是规模不经济。
Now revenue.
现在来看收益。
Total revenue is price times quantity; average revenue is the price; marginal revenue is the revenue from one more unit.
总收益等于价格乘以数量；平均收益就是价格； 边际收益是多卖一个单位带来的收益。
Normal profit is just enough to keep the firm in the industry, so it counts as a cost.
正常利润刚好足以让企业留在这个行业里， 所以它算作成本。
Supernormal profit is above it; subnormal is below, and that firm may leave.
超常利润高于它；次正常利润低于它，那家企业可能会退出。
Profit is highest where marginal revenue equals marginal cost.
利润在边际收益等于边际成本处最高。
A firm sells ten units at fifty pounds each.
一家企业以每件五十英镑卖出十件。
To sell an eleventh it must drop the price to forty-eight on EVERY unit.
为了卖出第十一件， 它必须把每一件的价格都降到四十八。
Total revenue at ten is fifty times ten, five hundred pounds.
十件时的总收益是五十乘以十，五百英镑。
At eleven it is forty-eight times eleven, five hundred and twenty-eight pounds.
十一件时是四十八乘以十一，五百二十八英镑。
So marginal revenue is the difference: twenty-eight pounds.
所以边际收益是两者之差：二十八英镑。
Stop and look at that.
停下来看看这个结果。
The eleventh unit sold for forty-eight, but it only added twenty-eight to revenue.
第十一件卖了四十八，却只给总收益增加了二十八。
The gap is because the lower price applies to ALL eleven units, not just the extra one — the firm lost two pounds on each of the original ten.
差额的原因是：降低后的价格适用于全部十一件，而不只是多出来的那一件—— 企业在原来的十件上每件少赚了两英镑。
That is why marginal revenue always falls faster than price.
这正是边际收益总是比价格下降得更快的原因。
Economists count profit differently from accountants, and this is the difference that catches students.
经济学家计算利润的方式和会计不同，而这个区别正是绊倒学生的地方。
An economist includes the opportunity cost of the owner's own resources — their time, their money — inside cost.
经济学家把所有者自身资源的机会成本——他的时间、他的资金——计入成本之内。
So normal profit, the amount just sufficient to keep the firm in the industry, counts as a COST, not as profit.
所以正常利润，也就是刚好足以让企业留在该行业的那个数额， 算作成本，而不算作利润。
Say that clearly in an answer.
在答题时要把这一点讲清楚。
Above it is supernormal profit, sometimes called abnormal profit.
在它之上是超常利润，有时也叫非正常利润。
Below it is subnormal profit, and a firm earning that will leave the industry in the long run.
在它之下是次正常利润，赚这个水平的企业在长期会退出该行业。
Every long-run entry-and-exit argument you will write rests on those three levels.
你将来要写的每一个关于长期进入与退出的论证，都建立在这三个层次之上。
Put the four structures on a single spectrum of competition, because that is how you should recall them.
把四种市场结构放在一条竞争程度的坐标上，因为你就应该这样去记它们。
At the left, perfect competition: very many firms, no barriers, an identical product.
最左端是完全竞争：企业非常多、没有壁垒、产品完全相同。
Then monopolistic competition: many firms competing on product differentiation, with low barriers.
接着是垄断竞争：企业很多，产品略有差异，壁垒较低。
Then oligopoly: a few large firms behind high barriers.
再往右是寡头垄断：少数几家大企业，处在高壁垒之后。
At the right, monopoly: one firm, very high barriers, a unique product.
最右端是垄断：只有一家企业、壁垒极高、产品独一无二。
Three questions place any market on this line — how many firms, how high the barriers, and how different the product.
三个问题就能把任何一个市场放到这条线上—— 有多少家企业、壁垒有多高、以及产品有多不同。
Firms sit in different market structures, ordered by competition.
企业身处不同的市场结构，按竞争程度排列。
At one end, perfect competition: many tiny price takers, an identical product, no barriers, normal profit only.
一端是完全竞争：许多小企业都是价格接受者，产品完全相同，没有壁垒，只有正常利润。
Next, monopolistic competition: slightly different products.
接着是垄断竞争：产品略有差异。
Then oligopoly: a few large firms that may collude in a cartel.
然后是寡头垄断：少数几家大企业，可能合谋组成卡特尔。
At the far end, monopoly: one seller, high barriers, supernormal profit.
另一端是垄断：只有一个卖家，壁垒很高，获得超常利润。
Read the perfectly competitive firm's long-run diagram.
来读完全竞争企业的长期图。
It is a price taker, so its demand is a horizontal line at the market price — average revenue and marginal revenue are the same line.
它是价格接受者， 所以它面对的需求是位于市场价格上的一条水平线—— 平均收益和边际收益是同一条线。
It produces where marginal cost equals marginal revenue, and in the long run that point sits exactly at the BOTTOM of average total cost.
它在边际成本等于边际收益处生产，而在长期，这一点恰好落在平均总成本的最低点。
Two consequences follow, and both are marks.
由此得出两个结论，而且都是得分点。
Price equals the minimum average cost, so it is productively efficient.
价格等于最低平均成本，所以它实现了生产效率。
And price equals marginal cost, so it is allocatively efficient too.
价格又等于边际成本，所以它同时也实现了配置效率。
It makes normal profit only, because any supernormal profit would attract entry that competes it away.
它只获得正常利润，因为任何超常利润都会吸引新企业进入，把它竞争掉。
Now the monopoly, and follow the order of operations, because this is where diagrams go wrong.
现在看垄断，并且要按操作顺序走，因为图正是在这里画错的。
The monopolist still produces where marginal cost equals marginal revenue — that fixes the QUANTITY.
垄断者仍然在边际成本等于边际收益处生产——这确定的是产量。
But it does not charge that value.
但它并不按那个值定价。
It goes UP from that quantity to the average revenue curve and charges the price buyers will actually pay.
它从这个产量往上走到平均收益曲线， 按买者实际愿意支付的价格来收费。
Price therefore sits above marginal cost, so the outcome is allocatively inefficient, and it is not at the bottom of average cost either.
于是价格高于边际成本，所以结果是配置无效率， 而且它也不在平均成本的最低点上。
The gap between price and average cost is supernormal profit, and high barriers to entry let the monopolist keep it indefinitely.
价格与平均成本之间的差额就是超常利润， 而高进入壁垒让垄断者可以长期把它保住。
Oligopoly has a feature the other three do not: interdependence.
寡头垄断有一个另外三种结构都没有的特征：相互依存。
With only a few large firms, each one watches the others, because any price change will be noticed and answered.
由于只有少数几家大企业，每一家都盯着其他家， 因为任何价格变动都会被察觉并被回应。
That leaves two routes.
这就留下两条路。
Price competition means cutting prices to win customers — effective, but a rival can match it, and both end up poorer.
价格竞争是靠降价来争夺顾客——有效，但对手可以跟进，结果两败俱伤。
So oligopolists often prefer non-price competition instead: advertising, quality, branding and service, which a rival cannot copy overnight.
所以寡头往往更偏好非价格竞争：广告、质量、品牌和服务， 这些是对手无法在一夜之间复制的。
The third possibility is that they stop competing and agree to fix prices.
第三种可能是它们干脆不竞争了，转而合谋定价。
That is collusion, and a group that does it is a cartel — illegal in most countries precisely because it turns an oligopoly into a monopoly.
这就是合谋，这样做的一伙企业就是卡特尔—— 在多数国家都是违法的，正是因为它把寡头垄断变成了垄断。
Price discrimination is charging different consumers different prices for the SAME good — a student train ticket next to a full-fare one, the same seat on the same train.
价格歧视是对同一种商品向不同消费者收取不同的价格—— 学生票和全价票并排出售，同一班车上的同一个座位。
Three conditions must all hold.
三个条件必须同时成立。
The firm needs price-setting power, so it cannot be a price taker.
企业需要有定价能力，所以它不能是价格接受者。
The groups must have different elasticities of demand, or there is nothing to exploit — students are more price-sensitive than commuters.
各类顾客的需求弹性必须不同，否则就没有可利用的空间—— 学生比通勤者对价格更敏感。
And the firm must be able to stop resale between the groups, or the cheap group simply buys and sells on, which is why the ticket carries a student card check.
而且企业必须能够阻止各类顾客之间的转售， 否则买得便宜的那一群人干脆买进再转卖出去， 这正是车票要查学生证的原因。
Get all three and the firm's profit rises.
三条都满足，企业的利润就会上升。
Compare them.
把两端比较一下。
A competitive firm is so small that price, average revenue and marginal revenue are one flat line.
完全竞争企业太小了，价格、平均收益和边际收益是同一条水平线。
In the long run it sits at the bottom of average cost: efficient, and normal profit only.
在长期，它位于平均成本的最低点：具有生产效率，只获得正常利润。
A monopoly faces the whole market demand, so marginal revenue lies below.
垄断企业面对整个市场的需求，因此边际收益位于需求之下。
It produces where marginal cost equals marginal revenue, then charges the higher price demand allows: that gap is supernormal profit.
它在边际成本等于边际收益处生产，然后按需求允许的更高价格出售。 这段差距就是超常利润。
Now the growth and survival of firms.
企业成长有两种方式。
They grow two ways: internal growth is selling more, external growth is joining another firm through a merger or a takeover.
内部增长就是卖得更多；外部增长是与另一家企业合并。 横向一体化是合并同一阶段的企业——两家汽车厂。
Horizontal integration joins the same stage — two car makers.
纵向一体化是合并不同阶段的企业——汽车厂收购轮胎厂。
Vertical joins a different stage — a car maker buys a tyre maker.
混合一体化是合并不同行业的企业，用来分散风险。
Conglomerate joins a different industry, to spread risk. Many firms stay small — survival, not growth, is the objective: a local market, an owner keeping control, a niche. The objectives of firms differ, and so does what counts as success.
很多企业仍然很小：市场是本地的、所有者想保持控制权，或者做的是利基市场。
Market power also allows price discrimination.
拥有市场势力还可以实行价格歧视。
Put external growth on a production chain and the three kinds of integration become obvious.
把外部增长放到一条生产链上，三种一体化就一目了然了。
Horizontal integration joins a firm at the SAME stage of the same industry — two car makers — which buys market share and economies of scale.
横向一体化是与同一行业中处于同一环节的企业合并——两家汽车制造商—— 这买来的是市场份额和规模经济。
Vertical integration joins a different stage — the car maker buys the tyre maker upstream, or the dealership downstream — which secures supply or secures an outlet.
纵向一体化是与不同环节的企业合并—— 汽车制造商向上游收购轮胎厂，或者向下游收购经销商—— 这保住的是供应或者销路。
Conglomerate integration joins a firm in a completely different industry, and the motive there is spreading risk, not efficiency.
混合一体化是与一个完全不同行业的企业合并， 其动机在于分散风险，而不是提高效率。
Name the motive as well as the type; the motive is usually where the marks are.
要把动机和类型一起说出来；分数通常在动机那里。
If big is cheaper, why does any small firm survive?
如果大企业更便宜，那小企业为什么还能生存？
Three reasons.
有三个原因。
Sometimes the market itself is small and local — a hairdresser cannot serve a customer two hundred miles away.
有时市场本身就是小而本地化的——理发师没法服务两百英里以外的顾客。
Sometimes the owner wants to keep control rather than grow.
有时是所有者宁愿保住控制权，也不想扩张。
And sometimes there are simply few economies of scale to be had in that trade.
还有些时候，那个行当本来就没有多少规模经济可言。
Small firms then survive on personal service or by filling a niche the big firms ignore.
于是小企业靠个性化服务，或者靠填补大企业不屑一顾的利基市场来生存。
One more idea belongs here and is often forgotten: barriers to EXIT, like costly machines that cannot be resold.
还有一个概念属于这里，而且常被遗忘：退出壁垒， 比如那些买来就转卖不掉的昂贵机器。
High exit barriers can trap a firm in a market where it is losing money.
高退出壁垒会把一家企业困在一个正在亏钱的市场里。
Finish with the reason a firm might not maximise profit at all.
最后来看企业为什么可能根本不去追求利润最大化。
In a large company the owners are the shareholders, but the managers run it — the divorce of ownership from control.
在大公司里，所有者是股东，但经营公司的是经理人—— 这就是所有权与控制权的分离。
That creates the principal-agent problem.
由此产生了委托代理问题。
The owners are the principals; the managers are their agents, hired to act for them.
所有者是委托人；经理人是他们的代理人，受雇替他们行事。
But the managers have their own aims: a bigger salary, a bigger department, an easier life.
但经理人有自己的目标：更高的薪水、更大的部门、更轻松的日子。
Because they hold the information and the day-to-day decisions, they can pursue those instead.
由于信息和日常决策都掌握在他们手里，他们可以转而去追求这些目标。
That single idea explains why a real firm might NOT maximise profit — and it is the link back to revenue maximisation, sales maximisation and satisficing.
这一个概念就解释了现实中的企业为什么可能不追求利润最大化—— 而它也正是回到收益最大化、销售最大化和满意化的那条线索。
What does a firm want?
企业想要什么？
The traditional answer is profit maximisation, where marginal revenue equals marginal cost.
传统的答案是利润最大化，在边际收益等于边际成本处生产。
Some chase revenue maximisation, where marginal revenue is zero.
有些企业追求收益最大化，在边际收益为零处生产。
Some chase sales maximisation, as much as they can at normal profit.
有些追求销售最大化，在仍能获得正常利润的前提下卖得越多越好。
Others just satisfice.
还有些企业只求满意。
And in a big company the owners are not the managers — the divorce of ownership from control, and the principal-agent problem.
而在大公司里，所有者并不是管理者：这种所有权与控制权的分离带来了委托代理问题。
Three habits that turn this topic into marks.
三个把知识变成分数的习惯。
First, on a cost diagram show marginal cost cutting average cost at its lowest point — examiners look for it.
第一，在成本图上要画出边际成本在平均成本最低点穿过—— 考官就找这一点。
Second, name the profit precisely: normal profit is a cost, supernormal profit is above it.
第二，把利润说准确：正常利润是一种成本，超常利润高于它。
Third, judge a market structure by the number of firms, the barriers and the price-setting power, not by size.
第三，判断市场结构要看企业数量、进入壁垒和定价能力，而不是看规模大小。