WEBVTT

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Here is a claim that sounds
wrong the first time you hear it.

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Two countries can both come out
ahead by trading with each other,

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even when one of them is worse
at making absolutely everything.

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Not one gains
and the other puts up with it.

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Both gain.

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So let me build the smallest
world I can get away with.

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Two countries, and I will call
them Home and Foreign, and two goods,

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cloth and wine.

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Both countries can make both goods,

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and the only resource either
of them has is hours of work.

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Here is the entire technology
of this world, in four numbers.

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How many hours it takes each country
to make one unit of each good.

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That is all the information there is.

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Take cloth first.

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Home turns out a unit
of cloth in two hours.

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Foreign needs six for the same unit.

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Now wine.

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Home needs four hours for a unit.

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Foreign, again, needs six.

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Read each line across.

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Two against six on cloth.

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Four against six on wine.

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Home wins on the top line,
and Home wins on the bottom.

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There is a name for that,
and we will get to it in a minute.

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But look at what it seems to imply.

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Home is faster at making everything
there is to make in this little world.

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So what could Foreign possibly sell?

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And why would Home ever buy anything,
when it can make both goods faster itself?

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It looks as though Home should make
everything it needs and keep to itself.

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That instinct is wrong. Not slightly
wrong, and not wrong in some special case.

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Both of these countries are going

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to end up with more cloth and more
wine than either can get on its own,

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and neither of them will work
a single extra hour to do it.

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The reason is that we
have been counting the wrong thing.

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Hours are not what
an economy really spends.

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So let me show you what it does spend.

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Let us give what we
just saw its proper name.

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When a country can make one unit of a good
in fewer hours than the other country can,

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we say it has an absolute
advantage in that good.

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Home needs two hours for a unit
of cloth against Foreign's six,

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so Home has an absolute
advantage in cloth.

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Home needs four hours for a unit
of wine against Foreign's six,

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so Home has an absolute
advantage in wine as well.

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Home holds both.

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And if absolute advantage were the thing
that decided who trades with whom,

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we would be finished already.

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Home would make everything,
Foreign would make nothing,

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and there would be no trade at all.

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But that is not what happens,
in this model or in the world.

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Foreign does exist, though.

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Foreign has workers, and those workers are
going to spend the week doing something.

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So the real question was never whether
Foreign can beat Home at anything.

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It is what Foreign
should do with the time it has.

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Here is what the hours are hiding.

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Nobody in Home is standing idle,
waiting for work to arrive.

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Every hour Home spends on wine
is an hour it did not spend on cloth.

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So take the four hours Home
needs for a unit of wine.

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There they are, from zero to four.

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Now, what else could Home
have done with them?

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A unit of cloth takes Home two hours.

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So four hours is not just four hours.

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Four hours is two whole units of cloth.

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Look at the picture.

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On top, those four hours buy
Home exactly one unit of wine.

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Underneath, the very same four
hours buy two units of cloth.

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Same hours, two different
baskets, and Home has to pick one.

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That is the real price of Home's wine.

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Not four hours.

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Two units of cloth that never got made.

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The receipt is written in hours,
but the economy pays in cloth.

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Economists have a name for that too,
and it is the one that matters.

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The opportunity cost of a thing
is what you gave up in order to get it.

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It is measured in goods, not in hours.

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And it is the number that is actually
going to decide who makes what.

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So let us go back

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to those four numbers and turn every
one of them into an opportunity cost.

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That is the table
that settles the whole question.

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Same two countries,
same two goods, same four numbers.

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But this time I am not
going to write down hours.

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I am going to write
down what one unit costs,

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measured in units of the other good.

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Start with cloth.

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One unit of cloth takes Home two hours.

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What else could Home
have done with those two hours?

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Wine costs four hours a unit,
so two hours buys half a unit of wine.

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So one unit of cloth costs
Home half a unit of wine.

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And Foreign?

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Six hours either way, so a unit of cloth
costs Foreign one whole unit of wine.

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There is the first row of the new table.

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Now turn it around and price the wine.

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One unit of wine costs Home four hours,
and four hours is two units of cloth.

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For Foreign it is six against six again,

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so a unit of wine costs it
exactly one unit of cloth.

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Look down Home's column for a moment.

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To make a unit of cloth it
sacrifices half a unit of wine.

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To make a unit of wine it
sacrifices two units of cloth.

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Those two numbers are reciprocals
of each other, and they always will be.

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There is the table that matters.

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And now the important move.

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Compare across each row,
not down the columns.

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Cloth first. Home gives up half
a unit of wine to make a unit of cloth.

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Foreign gives up a whole unit of wine.

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So cloth is cheaper in Home.

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Not faster.

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Cheaper.

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Home sacrifices less to get its cloth,

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and that is what we are going to call
having the comparative advantage in cloth.

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Now wine.

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Home gives up two units
of cloth to make a unit of wine.

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Foreign gives up one.

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Wine is cheaper in Foreign, and Foreign is
the country that is slower at making wine.

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Sit with that for a second, because it
is the hinge of the whole lecture.

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Foreign takes six hours
to make a unit of wine.

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Home takes four.

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Home is genuinely faster at it.

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But Home's four hours are expensive hours.

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Home is so good at cloth

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that every hour it moves to wine
throws away a great deal of cloth.

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Foreign's six hours are cheap hours,

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because Foreign was never going
to make much cloth with them anyway.

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So here is the definition
we actually need.

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A country has a comparative advantage
in a good when making one unit of it costs

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that country less of the other
good than it costs the other country.

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Home has the comparative
advantage in cloth.

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Foreign has the comparative
advantage in wine.

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And notice the shape of that result.

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Unless the two countries
have identical opportunity costs,

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each of them has the comparative
advantage in exactly one good.

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You cannot
be comparatively better at both.

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Being cheaper at cloth is the very
same statement as being dearer at wine.

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It is one ratio, read in two directions.

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Time to draw this.

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Wine along the bottom, cloth up the side.

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Every point in here is a basket:
so much wine, so much cloth.

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Home has two hundred
and forty hours of work in a week.

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Put every one of them
into cloth, at two hours a unit,

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and Home makes a hundred and twenty
units of cloth and no wine at all.

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Put all of them into wine instead,

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at four hours a unit, and Home makes
sixty units of wine and no cloth.

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That is this corner,
down on the wine axis.

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Every split in between is available too,

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and all of them lie on the straight
line joining those two corners.

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That line is Home's
production possibility frontier.

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Take a point on it. Thirty units
of wine and sixty units of cloth.

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Sixty cloth is a hundred and twenty hours,
thirty wine is another hundred and twenty,

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and there are the two hundred and forty.

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It fits exactly.

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On the frontier every hour
is used and nothing is wasted.

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Inside it Home is idling.

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Outside it Home simply cannot go, because
there are not enough hours in the week.

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Foreign now.

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Foreign has three hundred hours,
and six hours a unit either way.

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All cloth is fifty units.

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All wine is fifty units.

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Its frontier
is this shorter line down here.

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And there is the paradox,
drawn out in full.

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Home's frontier lies
entirely outside Foreign's.

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Every basket Foreign can produce,
Home could produce with hours to spare.

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Which is exactly what
makes the result surprising.

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If this picture were all you ever saw, you
would say Foreign has nothing to offer.

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The two lines do not even cross.

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Now suppose there is no trade at all.

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Each country has to make
everything it consumes.

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Say Home settles on eighty units
of cloth and twenty units of wine,

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right there on its frontier.

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And Foreign settles on thirty units
of cloth and twenty units of wine,

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right there on its own.

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Both of them are doing
the best they can alone.

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No wasted hours,
nothing left on the table.

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Add the two together.

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The world, all in,

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is producing a hundred and ten units
of cloth and forty units of wine.

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Hold on to those two numbers.

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Both of those numbers are about to go up.

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Nobody is going to work an extra hour.
Nobody is going to learn anything new.

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And both of them go up.

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Here is the same picture,
and the same two no-trade baskets.

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Home at eighty cloth and twenty wine.
Foreign at thirty cloth and twenty wine.

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Now let us do what the opportunity
cost table told us to do.

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Home gives up less to make
cloth, so Home should make cloth.

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Foreign gives up less to make
wine, so Foreign should make wine.

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Not a bit more of each.

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All of it.

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Each country puts every hour it

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has into the single good it
sacrifices least to produce.

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Which already sounds reckless.

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Home is better at wine than Foreign is,

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four hours against six, and I am telling
Home to stop making wine entirely.

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That is precisely
the move that feels wrong,

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and it is the move
the whole result depends on.

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Speed is not the test. Sacrifice is.

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Home is now all the way up its own
frontier, at the cloth corner.

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A hundred and twenty units
of cloth, and not a drop of wine.

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And Foreign is at the other
extreme, down in its wine corner.

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Fifty units of wine,
and not a scrap of cloth.

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Nothing magic happened there.

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Nobody worked an extra hour.

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Nobody invented a better loom.

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Each country simply stopped
doing the thing it was bad at,

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in the opportunity cost sense,
which is the only sense that counts.

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Now add the world up again.

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Cloth: a hundred and twenty units,
where before there were a hundred and ten.

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Wine: fifty units,
where before there were forty.

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Ten more units of each good,
out of exactly the same labour.

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And notice where that came from.

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Not from working harder.

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It came from moving
each hour to the country

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where spending it throws away the least.

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That is the first half of the argument,
and it is the easier half.

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There is more stuff in the world.

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But the world does not eat.

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Look at where these two
countries actually are.

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Home is sitting on a mountain
of cloth with nothing to drink,

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and Foreign has a lake
of wine and nothing to wear.

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Measured against where they started,

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both of them are worse
off at this exact moment.

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Specialization on its own is not the gain.

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It is half a step.

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So let them trade.

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Home is holding a hundred
and twenty units of cloth.

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Foreign is holding fifty units of wine.

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Now they trade, and the only
question left is at what rate.

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The exchange rate they agree
on is called the terms of trade.

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Any rate strictly between
their two opportunity costs is one

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that both countries will accept.

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So write down the two bounds first.

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Foreign gives up one
cloth for a unit of wine.

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Home gives up two cloth
for a unit of wine.

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Below one cloth per unit of wine,

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Foreign would rather keep
its wine and weave its own cloth.

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Above two, Home would rather keep
its cloth and press its own wine.

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Strictly in between, both say yes.

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So let us pick a rate in the middle.

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Three units of cloth
for every two units of wine,

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which is one and a half cloth per wine.

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Comfortably between one and two.

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Before we move anything, put the old
no-trade baskets back on the picture.

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Those are the two points to beat,

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and we will be writing
their numbers down in a moment.

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Home ships thirty-six units
of cloth across the water,

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and gets twenty-four units of wine back.

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Check the rate: thirty-six
over twenty-four is three over two.

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That is the agreed price.

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So what does Home end up holding?

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Start with the line to beat.

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Without any trade at all, Home
consumed eighty cloth and twenty wine.

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It produced a hundred and twenty
cloth, gave thirty-six of them away,

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and that leaves eighty-four.

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And it received twenty-four units
of wine. Watch where that puts Home.

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Compare the two lines. Eighty-four
beats eighty. Twenty-four beats twenty.

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Home has more of both goods.

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And look where that dot is now sitting.

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It is outside Home's own frontier.

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There is no way to split two hundred
and forty hours that produces that basket.

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Home cannot make it, but Home can have it.

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That dashed line is what Home
can now consume. Start from the corner

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where it produces, and trade along
it at one and a half cloth per wine.

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It sits above the frontier
everywhere except at the corner itself.

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Now do the same for Foreign.

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Without trade it consumed
thirty cloth and twenty wine.

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It produced fifty units of wine, gave
away twenty-four, and keeps twenty-six.

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In return it received
thirty-six units of cloth.

00:14:45.612 --> 00:14:50.385
Thirty-six cloth and twenty-six wine,
against thirty and twenty before.

00:14:50.581 --> 00:14:55.016
Foreign, the country that is slower
at cloth and slower at wine, the country

00:14:55.016 --> 00:14:59.557
that loses on every single line
of the hours table, has six more of each.

00:15:00.353 --> 00:15:03.396
And its dot is outside its frontier too.

00:15:03.499 --> 00:15:06.865
Both of these dashed lines
are consumption possibilities,

00:15:06.948 --> 00:15:10.617
and both of them lie above what
the country can actually produce.

00:15:11.491 --> 00:15:12.953
So there it is.

00:15:13.036 --> 00:15:17.190
Both countries ended up with more
of both goods. Nobody worked longer.

00:15:17.273 --> 00:15:19.117
Nobody got better at anything.

00:15:19.200 --> 00:15:22.719
The only thing that changed
is who spent their hours on what.

00:15:23.515 --> 00:15:28.204
That is comparative advantage, and it is
why the claim sounds wrong and is right.

00:15:28.287 --> 00:15:29.795
Trade is not a race.

00:15:29.878 --> 00:15:34.882
What a country sells is not its speed.
It is the thing it gives up least to make.

00:15:35.679 --> 00:15:39.210
One last thing, so you know
where the argument stops.

00:15:39.406 --> 00:15:42.960
Suppose the two countries
had identical opportunity costs.

00:15:43.156 --> 00:15:47.464
Suppose a unit of wine cost two
units of cloth in both places.

00:15:48.261 --> 00:15:51.141
Then there is no rate
strictly between them.

00:15:51.245 --> 00:15:55.236
There is no price both would accept,
and there is nothing to gain.

00:15:55.319 --> 00:15:58.650
The gain from trade is made out
of the difference in opportunity costs,

00:15:58.733 --> 00:16:00.382
and out of nothing else.