When there aren't gains from trade

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When there aren't gains from trade발음듣기

[Instructor] So let's say we're in a very simplified world where we have two countries, Country A and Country B .발음듣기

And they're each capable of producing apples or bananas or some combination of them and what this chart tells us if Country A put all their energy behind apples in a day they could produce three apples.발음듣기

And if they put all of their energy behind bananas in a day they could produce six bananas.발음듣기

Similarly, Country B, if they put all of their energy behind apples in a day they could produce two apples and Country B if they put all of their energy behind bananas in a day they could produce four bananas.발음듣기

So given this, who has the comparative advantage in apples and who has the comparative advantage in bananas and how should they trade?발음듣기

Pause this video and try to figure it out on your own.발음듣기

All right so when we're thinking about comparative advantage we really want to think about well, what is the opportunity cost of producing an apple in each country and what is the opportunity cost of producing a banana in each country?발음듣기

And so let me make another little sub column right over here.발음듣기

Opportunity cost, and so what is the opportunity cost of an apple in Country A?발음듣기

And pause this video at any point if you get inspired.발음듣기

Well, to produce three apples they would have to trade off six bananas.발음듣기

And so that means that per apple they are not producing two bananas.발음듣기

So this is two bananas, two bananas.발음듣기

I'll just write bana, bananas per apple.발음듣기

And their opportunity cost for bananas is just going to be the reciprocal of that.발음듣기

So one over two apples, apples per banana and then for Country B we can do a similar calculation and you might be noticing something interesting is about to happen.발음듣기

What's Country B's opportunity cost of apples?발음듣기

Well, one way to think about it if they produce two apples that means they're giving up four bananas.발음듣기

Or they're giving up two bananas per apple.발음듣기

So two bananas, bananas per apple.발음듣기

And once again, if we want to think in terms of the opportunity cost of a banana well, to produce four bananas they're giving up two apples.발음듣기

So this is one half of an apple per banana.발음듣기

Per, I'll just write, banana right over there.발음듣기

So this one is a little bit interesting.발음듣기

They have the same opportunity cost for apples in terms of bananas, and they have the some opportunity cost for bananas in terms of apples.발음듣기

And so because they have the same opportunity costs.발음듣기

So let me write this down, same opportunity costs.발음듣기

There is no comparative advantage.발음듣기

So no comparative advantage in either.발음듣기

Advantage in either.발음듣기

And so based on our very simple model here there are no gains from trade.발음듣기

Another way we could visualize this that maybe makes it maybe hopefully a little bit more clear.발음듣기

So let me make one axis here.발음듣기

I'm trying to draw a straight line, all right.발음듣기

And then this is my other axis right over here.발음듣기

And let's make this one right over here, this horizontal one let's make this the apples axis and let's make the vertical one the bananas axis.발음듣기

And we're saying per day and this of course is apples per day and so if we look at Country A.발음듣기

Let me do Country A in a new color.발음듣기

So Country A, let's say orange.발음듣기

If they put all their energy behind apples they could produce one, two.발음듣기

Let me spread this out a little bit.발음듣기

They could produce one, two, three apples in a day.발음듣기

If they put all their energy behind bananas they could produce, let's just say this is two, four, six.발음듣기

So that's six, this is four, this is two.발음듣기

This is three right over here.발음듣기

Let me put markers in-between to make this clear.발음듣기

So if they put all of their energy into bananas they could produce six in a day.발음듣기

And so their production possibilities if we assume it is a linear trade-off would look something like this and the slope right over here this would be the opportunity cost.발음듣기

So the slope right over here, every time we increase apples by one we decrease bananas by two.발음듣기

So in this situation, we would have, so the slope here is equal to, well, it's actually a negative slope.발음듣기

It's equal to negative two bananas, bananas per apple.발음듣기

So this right over here, this slope based on how I picked the axes this is giving me the opportunity cost for apples in terms of bananas.발음듣기

Every time I increase an apple how many bananas am I actually giving up?발음듣기

So that is my opportunity cost there.발음듣기

And now if we think about Country B.발음듣기

Let me do this in a new color.발음듣기

I'm running out of colors.발음듣기

Country B right over here they could either produce four bananas or two apples or things in-between.발음듣기

But notice, it has the exact same slope The slope is the opportunity cost.발음듣기

And if we switch these axes right over here then the slope would be the opportunity cost for bananas in terms of apples.발음듣기

But the big takeaway here if you see the production possibilities of two countries.발음듣기

And we're talking about two goods and they have the same slope then that means their opportunity costs are going to be the same, and there's not going to be a gain from trade.발음듣기

Remember, the whole point of comparative advantage and trading is that both countries will benefit.발음듣기

That's really the big takeaway here.발음듣기

But there are situations where both countries wouldn't benefit because they have the same opportunity cost and this was an example of one of them.발음듣기

Now the other case, sometimes one will have a comparative advantage over the other.발음듣기

They do have different opportunity costs and then you might have no gains from trade.발음듣기

Maybe there's some way that they can't know each other's opportunity costs.발음듣기

There's some way that they don't trade.발음듣기

Maybe irrespective of what the models tell us about comparative advantage some country says hey, I don't want to produce bananas.발음듣기

Apples are the future, that's a higher skilled industry whatever else, so there's definitely scenarios especially even in our model, in our very simplified model where there might not be gains from trade.발음듣기

And the classic one of course is when there's no comparative advantage and both countries have the same opportunity costs in the goods.발음듣기

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