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LostInParadise's avatar

What is the Law of Comparative Advantage?

Asked by LostInParadise (32183points) July 20th, 2009

I know in vague terms what the law says. If there are two nations producing goods, even if one can produce everything more efficiently than the other, there is still something that second nation can produce better in comparison to everything else that it produces and to achieve maximum productivity between the two nations that commodity is what the second nation should concentrate on.

I have searched the Web for something a little clearer but have not found anything. Here is how I have reasoned on this. Suppose we have commodities x1, x2, x3 and x4. Let f(x) be the productivity for nation 1 and g(x) be the productivity for nation 2. It is not hard to show mathematically that there is some x among x1, x2, x3 and x4 such that f(x)/f(xi) >= g(x)/g(xi), where xi ranges from x1,..,x4. I chose 4 to be concrete, but the same reasoning applies to any number of goods. Is this what is meant by comparative advantage?

One problem that I have with this is that it does not work for more than two nations. If there is a third nation with productivity function h(x), then, from the above, there is some y such that f(y)/f(xi) >= h(y)/h(xi). The problem is that the x and y are not necessarily the same. The commodity that gives the greatest advantage against one nation would not necessarily be the same commodity that gives the greatest advantage over the other.

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7 Answers

jrpowell's avatar

You are over-thinking things. All it really says is that one country can make things cheaper. The concept of ceteris paribus is applied heavily in economics. It pretty much means that economist go insane if they take every little thing into account. Sometimes you have to make calculations with as few variables as possible.

LostInParadise's avatar

Could you state this algebraically?

jrpowell's avatar

Nope. It really isn’t something that you can do that with. It is a concept. It isn’t math.

swuesquire's avatar

I don’t know about stating it algebraically, but here’s a post from Mankiw’s micro econ book that explains it with two nice graphs and a chart. http://books.google.com/books?id=cNZMGdsJ2HMC&pg=PA50&lpg=PA50&dq=comparative+advantage+chart+mankiw&source=bl&ots=t9ThPCod7q&sig=4huTEuyhhf1xcwPB5BKZpp8Mogk&hl=en&ei=xaVkSuTmH4mKMcKmjPgB&sa=X&oi=book_result&ct=result&resnum=1

I’m not sure if these links preserve page numbers, but the part you want to look at is on pages 49 and 50. I found these charts very helpful back when I was taking intro to econ courses.

swuesquire's avatar

@JohnPowell: It’s not just that one country can make things cheaper. It’s that both countries benefit when they make whatever they can make more easily and trade. It’s supposed to be a positive sum game.

LostInParadise's avatar

I think I kinda had the right idea. With two products and two producers, you produce the product whose ratio to the other product is bigger than that of the other guy. Unless the ratios are equal, this will have to hold true. If the producer one’s productions are p1 and q1 and producer two’s productions are p2 and q2 then either p1/q1 > p2/q2 or else q1/p1 > q2/p2.

I can see how this can be extended to multiple producers of two products. Depending on the demand for the products, the producers with second or third largest ratio might choose the product. I do not see how things play out with more than two products.

swuesquire's avatar

Your ratios sound like the way opportunity costs are determined. If p1/q1>p2/q2, and you are producer 1, it would make sense for you to produce item p and buy them from producer 2 instead of trying to produce the item on your own, because you would give up less in trading than you would in producing the product yourself. (I think I have that right, but it may be the other product that you want to trade. RATIOS!!!). Anyways, at this point I get lost. Price adjustments and stuff would enter in to balance out production (and that would extend to multiple producers and products), but honestly, my knowledge of microeconomics is not the best.

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