我们一直在考虑橙汁市场 We've now thought a lot about the orange juice market
前几节我们从公司层面考虑了 At least in the firm specific level in the last few videos, we talked about
经营橙汁公司的平均总成本 平均可变成本和边际成本 what our average total cost and average variable cost and marginal cost
经营橙汁公司的平均总成本 平均可变成本和边际成本 are when we are running an orange juice making business
下面从市场层面考虑问题 Now let's think about what happens at the market level
我们将回头使用之前学过的 So we're gonna go back to something we though about in the past
供给和需求曲线的知识 in terms of just supply and demand curves
这是橙汁市场 So this is the orange juice market
我画一下需求和供给曲线 And let's just draw some supply and demand curves here
这是每加仑的价格 So this is going to be the price per gallon
假设这是1美元 Let's say this right over here is one dollar
这是50美分 This right over here is $.50
这是0 And this is 0
假设这是量 And let's say that this is the quantity
以每周的加仑数计 in gallons per week
我们这里考虑整个橙汁市场 And we're gonna talk about the entire orange juice market
所以 这里的单位是百万加仑/周 So this is going to be in millions of gallons per week
刻度是1 2 3 4 5 6 And this is 1, 2, 3, 4, 5, and 6
让我简化一下 同上一节视频关联起来 And let me just simplify relative to what we saw in the last video
假设橙汁市场的供给曲线… let's say that the supply curve for the orange juice market --
我得小心一些 这是短期供给曲线 I'll be careful this time. This is the near-term supply curve or the short-term supply curve
它是这样的 It looks something like this
这是供给曲线 That is the supply curve
这是整个市场 所有橙汁生产者都在其中 This is the entire market. These are all of the orange juice producers
要让他们生产第一加仑橙汁 So even to get them to produce that first gallon
你需要让他们获得20美分 it looks like they need about $.20 for that first gallon
而后面每一加仑增量 他们会要更多钱 And then each incremental gallon, they need more and more money
整个市场上 这一加仑增量的边际成本会不断提高 The marginal cost of that incremental gallon
整个市场上 这一加仑增量的边际成本会不断提高 for the market as a whole is going higher and higher and higher
他们从更远地方买橙子 需要更多运输费用等等 They get oranges from further away and transport them further and further
这里是供给曲线 So this right over here is the supply curve
或者你也可以把它看成边际成本曲线 Or you can view it as the marginal cost curve
这里我随便画一条需求曲线 Now let's just draw an arbitrary demand curve here
需求曲线大概是这样 The demand curve looks something like this
这是当前需求曲线 That's our current demand curve
下面我要加入一个价格 And now I'm going to add to this the price
这个价格上 供给橙汁的公司 at which firms, the suppliers of the orange juice
在经济利润上中立 或者说经济利润为0 make them neutral in terms of economic profit or when economic profit is equal to zero
假设这里 也就是当前均衡价格 So let's say right over here which happens to be our current equilibrium price
价格是每加仑50美分 This is the price, $.50 per gallon
这是经济利润为0时的价格 This is the price at which economic profit is zero
回想一下 经济利润为0和会计利润为0不是一回事 I want to remind you, economic profit being 0 doesn't mean that the accounting profit is 0
这个价格下人们可以赚钱 People could be making money at this price
只不过是否做这门生意而言 人们是中立的 It just says that they're neutral whether or not they should be doing this business
他们所赚的钱 The amount of money that they're making
同他们做其它事的机会成本一样大 is roughly comparable to their opportunity cost to be doing other things
我这里说经济利润为0 So when I say economic profit is zero
这有时也叫作正常利润 sometimes that's called the normal profit or economic profit is zero
说的是此价格上 关于开不开公司 人们态度中立 this is the price at which people are neutral between shutting down and starting up a business
如果经济利润为正 If your have positive economic profit
很多人会进入这个市场 that means that more people want to go into this market
如果经济利润为负 If you have negative economic profit
很多人希望快点用完固定成本 that means people are going to want essentially use up their fixed expenses
包括设备 劳动合同这些 然后退出 their equipment and any labor contracts that they might have and then go out of business
这就是那一点 So this is that point right over there
下面考虑几种情形 假设有研究报告出炉 Now think of a couple of scenarios. Let's say a research paper comes out
出于某种理由 报告说橙子对身体有害 And in that research paper for whatever reason, we don't know if it's a well-done research
出于某种理由 报告说橙子对身体有害 it says oranges are bad for you for whatever reason
出于某种理由 报告说橙子对身体有害 So the research paper comes out and says oranges are bad for you
这时需求会怎么变化 任意价格处需求都会下降 What happens to demand? Well, at any given price demand will go down
新需求曲线会像这样 And the new demand curve might look something like this
短期来看 我们得到新均衡价格和均衡量 Now the near-term, we have a new equilibrium price and a new equilibrium quantity
这是老均衡价格 This was the old equilibrium price
根据我的设置 这里假设经济利润为0 The way I've set up, it would just happen to be the price at which economic profit is 0
这是老均衡量 略大于一周3百万加仑 This was a old equilibrium quantity, a little over 3,000,000 gallons a week
现在 新的均衡价格降低了 大概是每加仑40美分 Now we have a new lower equilibrium price which looks like about $.40 per gallon
均衡量也降低了 and we have a new lower equilibrium quantity
这时会发生什么 Now what happens at this price?
显然 短期来看 人们还会继续生产 Obviously in the near-term, people are willing to produce there
因为他们的边际成本在这里 because that's where their marginal cost is
之前视频中我们考虑过 So as we saw in multiple videos that
人们会一直生产 直到价格等于边际成本 someone's willing to produce when the price is equal to their marginal cost
他们会继续生产 So they're willing to produce a quantity up to
直到边际成本等于边际收入 或者说价格 when their marginal cost = the marginal revenue or the price that they're going to get
但是 他们需要获得50美分才能获得经济利润 But I just said, they need to get $.50 a gallon in order to make an economic profit
而现在价格只有每加仑40美分 Now if they get to about $.40 a gallon
他们会承受经济损失 they're going to be having an economic loss
这里没有利润 So no profit there
如果没有利润 And if there's no profit there
他们没有理由继续待在这个行当里面 it really doesn't make sense for all of them to continue in that business
随着时间的推移 他们会退出 So what's going to happen is that over time
当然 他们会在短期继续生产 it will make sense for them in the near-term to produce
毕竟这里存在固定成本 to use up -- they've already put in their cost
设备和劳动合同这些 for their equipment and maybe labor contracts and whatever else
但随着价格一直很低 but over time when prices are this low
人们用完设备这些后 就没有理由继续买新设备了 as people use up their equipment, there is no incentive for them to buy new equipment
劳动合同到期后 就没有理由续签新合同了 As a labor contract expires, there's no incentive for them to renew the labor contract
这些到期后 他们会停止生产 As those things expire, they're just going to shut down the business
停止生产后 会发生两件事 And so as they shut down the business, 2 things will happen
一是市场产量下降 二是价格上升 Quantity produced in the market will go down and the price will go up
我们会沿这条曲线到这一点 We will essentially move along this curve until we get to this point
这时 每加仑价格又是50美分了 That's the point once the price is at $.50 a gallon again
人们又变得中立起来 他们不会关闭公司 then people are neutral now; they're not going to shut down their firms
长期来看 我们会到这个新均衡量和新价格 So we'll get to this new equilibrium price and equilibrium quantity in the long term
考虑另外一种情形 Now let's think of another situation
报道不是说橙子有害 instead a newspaper report saying that oranges are bad
而是说橙子有益健康 let's say a newspaper report comes out saying oranges are very good
能延年益寿 是最好的食物 They make you live longer; they are the best thing that you can have
那么任意价格处 需求量都会上升 Well then at any given price, you're going to have more demand
需求曲线会像这样 And so you would have a demand curve that looks something like that
均衡量和均衡价格都会更高 And then you'd have a higher equilibrium quantity and a higher equilibrium price
由于价格高于经济利润为0时的价格 And since the price is higher than the price at which the economic profit is 0
人们会得到正经济利润 于是很多人都想进入这个行业 people are going to be making very positive economic profit
人们会得到正经济利润 于是很多人都想进入这个行业 which means that there is a strong incentive
人们会得到正经济利润 于是很多人都想进入这个行业 the people were neutral between shutting down the business or starting up the business
人们会得到正经济利润 于是很多人都想进入这个行业 At that point a lot of people are strongly motivated to enter into the business
于是越来越多的人 So what's going to happen is more and more people
购买越来越多的设备 招越来越多的人 are going to get more and more equipment and hire more and more people
于是量会上升 而价格会减少 And as I do that, the quantity is going to go up and the price is going to go down
长期来看 我们又会回到这条线上 and so over the long-term you're going to shift back to this line
价格回到这里以后 Once the price gets down to that
不会有很多人进入 人们变得中立 then there's no reason for more people to enter; they're kind of neutral about it
也就是说短期而言 So what you're seeing happening is in the short term
你可以考虑需求曲线和短期供给曲线的交点 you would look at where the demand curve intersects with a short-term supply curve
但长期而言 你要考虑它同水平线的交点 But in the long-term, you care where it intersects with this horizontal line which is
也就是经济利润为0的直线 the price at which economic profit is 0
也许这样考虑 比之前几节视频所说的更准确 And that's why you'll hear -- and this is a more precise way of thinking about it
也许这样考虑 比之前几节视频所说的更准确 than what we've done in the previous videos
这条水平线 可以考虑为长期供给曲线 This horizontal line right over here, you can view this as the long-run supply curve
也就是说 不管发生什么 and that says look, pretty much whatever
长期来看 我们总会生产需要的供给量 over the long run, we will always produce whatever supply is necessary
到经济利润为0时 人们就会态度中立 given that people are neutral when it comes to economic profit
到下面这里 人们会用完所有固定成本 You go down here, yes people will try to use up their fixed costs
但用完固定成本后 他们就没理由继续做了 but once they used up their fixed costs, no incentive for them to stay in business
有些人会退出 价格上升 供给量下降 and some of them go out of business; price goes up; quantity goes down
你又回到长期供给曲线和需求曲线相交的地方 you get back to the long-run supply curve and where that intersects with the demand curve
相反 如果经济利润丰厚 很多人进入市场 Or if the opposite happens, a lot of economic profit, a lot of entrance into the market
价格下降 供给量上升 price goes down; supply goes up
还是回到长期供给曲线和需求曲线相交的地方 you get back to the long run supply curve. Or you could say, you go back to where the
还是回到长期供给曲线和需求曲线相交的地方 new demand curve is intersecting the long-run supply curve