Growing cars in Iowa

[T]here are two technologies for producing automobiles in America. One is to manufacture them in Detroit, and the other is to grow them in Iowa.

Here's the detailed technology by which you grow cars in Iowa:

First you plant seeds, which are the raw material from which automobiles are constructed. You wait a few months until wheat appears. Then you harvest the wheat, load it onto ships, and sail the ships eastward into the Pacific Ocean. After a few months, the ships reappear with Toyotas on them.

Who could object to such a nice technological alternative?

Today, I am beginning to teach trade in my Principles of Economics class. This is a classic folk description of international trade first advanced by David (son-of-Milton) Friedman and then quoted by Steven Landsburgh (the source of the quotes here) in his marvelous book The Armchair Economist. David quoted it again in his own book Hidden Order: the Economics of Everyday Life.