NARRATOR: Listen to part of a lecture in an economics class. The professor has been talking about international trade.

旁白：听一段经济学课程中的讲座。教授一直在谈论国际贸易。

FEMALE PROFESSOR: Ok. So let's recap from yesterday. Why do nations engage in international trade? Well, it's often because they have a surplus, more than they need, and they also trade for the opposite reason when they have shortages and can't produce everything they want or need domestically.

女教授：好的，让我们回顾一下昨天的内容。为什么国家会参与国际贸易？通常是因为他们有盈余，比他们需要的多，他们也因为相反的原因进行贸易，当他们有短缺时，无法在国内生产他们想要或需要的一切。

So these explanations are good as far as they go. But there's another scenario we need to discuss. And that is, what if a country is capable of producing something it wants or needs, but it can also import that same product from another country.

所以这些解释在某种程度上是好的。但我们需要讨论另一个情况。那就是，如果一个国家有能力生产它想要或需要的东西，但它也可以从另一个国家进口同样的产品。

FEMALE PROFESSOR: Now, how does the country decide whether to make the product itself or import it? Ok, take an example.

女教授：现在，国家如何决定是自己生产还是进口呢？好的，举个例子。

Think about the bananas that you buy in the supermarket. If you look closely, you'll see that most bananas in the United States are imported, imported from countries with tropical climates.

想想你在超市买的香蕉。如果你仔细观察，你会发现美国的大部分香蕉是进口的，来自有热带气候的国家。

But the United States has warm regions. It has green houses. Clearly, it would be possible to grow bananas here. So why doesn't the US do that? Scott?

但美国有温暖的地区，有温室。显然，这里也有可能种植香蕉。那么为什么美国不这样做呢？斯科特？

MALE STUDENT: Well,it's like a lot cheaper and more efficient for countries with tropical climates, for tropical countries to grow bananas, isn't it? I mean, they don't need greenhouses to grow bananas, and they're not so limited to certain regions.

男学生：对于有热带气候的国家来说，种植香蕉更便宜、更高效，不是吗？我的意思是，他们不需要温室来种植香蕉，而且他们不受某些地区的限制。

FEMALE PROFESSOR: Ok, good. That's exactly right. Tropical countries have what we call an absolute advantage in producing bananas.

女教授：很好，完全正确。热带国家在种植香蕉方面具有我们所谓的绝对优势。

Absolute advantage is the term we use when a country can produce more of a product using fewer resources.

绝对优势是指一个国家可以用更少的资源生产更多的产品。

They're the most efficient producer of something. And the United States can't be that with bananas. So it's better off specializing in other goods that it can make more efficiently.

他们是某样产品最高效的生产者。而美国在香蕉方面无法做到这一点。所以它最好专注于其他可以更高效生产的商品。

FEMALE PROFESSOR: Let's take an example. Say we have two countries and say they each make only two products, and they trade only with each other. Simplistic, I know, but, well, you'll see where I'm going with this in a moment.

女教授：让我们举个例子。假设我们有两个国家，假设他们各自只生产两种产品，并且他们只与彼此进行贸易。我知道这很简单，但你马上就会明白我的意思。

So, as I was saying, two countries, two products, one country can produce both products more efficiently than the other country. Should these two countries even trade at all?

所以，正如我所说，两个国家，两种产品，一个国家可以比另一个国家更高效地生产这两种产品。这两个国家是否应该进行贸易？

FEMALE STUDENT: Em..well,no. I mean, like what's in it for the more efficient country?

女学生：不……对效率更高的国家有什么好处？

FEMALE PROFESSOR: Well,what is in it for them? Let's call these countries, X and Y. Country X makes both TVs and chairs more efficiently than country Y does. It has an absolute advantage in producing both commodities, no question. But what economists also look at is relative efficiency.

女教授：对他们有什么好处？让我们称这两个国家为x和y。国家x在生产电视和椅子方面比国家y更高效。它在生产这两种商品方面具有绝对优势，毫无疑问。但经济学家还关注相对效率。

And from that perspective, we see that country X is a lot more efficient at making TVs than it is at making chairs. And in country Y? Well, it turns out they're more efficient at making chairs than TVs.

从这个角度来看，我们发现国家x在生产电视方面比生产椅子更高效。而在国家y？结果发现他们在生产椅子方面比生产电视更高效。

So we say that country y has a comparative advantage at chair making and country x has a comparative advantage at TV making.

所以我们说国家y在生产椅子方面具有比较优势，而国家x在生产电视方面具有比较优势。

FEMALE PROFESSOR: So what should happen? Well, first, both countries should specialize in the production of just one thing, the product they are most efficient at making. Country x should make only TVs. And country y should make only chairs, then, the two of them should trade. Specialization and trade are going to lead to increases in production and increase overall supply of goods and generally lower prices. Right?

女教授：那么应该发生什么？首先，两国应该专门生产一种产品，他们最擅长生产的产品。国家x应该只生产电视。国家y应该只生产椅子，然后两国进行贸易。专业化和贸易将导致生产增加，整体商品供应增加，通常价格下降。对吧？

MALE STUDENT: Professor, I still don't see how countries figure out when and where they have a comparative advantage.

男学生：教授，我还是不明白国家如何确定他们在何时何地具有比较优势。

FEMALE PROFESSOR: You can't fully understand the concept of comparative advantage without also considering the related concept of opportunity cost.

女教授：如果不考虑与之相关的机会成本概念，你就无法完全理解比较优势的概念。

Opportunity cost is what you lose, the options you have to give up in order to use your time and resources for something else, countries can determine where their comparative advantages lie, like making TVs instead of chairs, by figuring out what they can make with the lowest opportunity cost.

机会成本是你为了将时间和资源用于其他事情而失去的东西，你必须放弃的选择。国家可以通过找出他们能以最低机会成本生产的东西来确定他们的比较优势所在，比如生产电视而不是椅子。

Well, you know, maybe this will be clear if we apply it on a personal level.

也许如果我们在个人层面上应用它，这会更加清晰。

FEMALE PROFESSOR: Now think about when you go out to a movie, your direct monetary cost is the price of the movie ticket, right? But you also spend two hours at the theater.

女教授：现在想想你去看电影的时候，你的直接货币成本是电影票的价格，对吧？但你也花了两个小时在影院。

Your opportunity cost includes both whatever else you could have spent your money on, 10 candy bars may be, and whatever else you could have accomplished during the time you were watching the movie.

你的机会成本包括你本可以用这些钱买的其他东西，可能是10块糖果，以及你在看电影期间本可以完成的其他事情。

You might have completed your homework for this class. Or you might have worked two hours overtime at your job, thereby earning instead of spending money. See these lost possibilities are your opportunity cost.

你可能已经完成了这门课的作业。或者你可能加班了两小时，从而赚了钱而不是花钱。看到这些失去的可能性就是你的机会成本。