Thinking about the categories "tradable" and "non-tradable"

People seem to underestimate the amount of manufacturing in the United States. According to Wikipedia, U.S. manufacturing is 19 percent of the world total. But this got me to thinking about classifications of economic activities.

It used to be that a country exported primary products (from agriculture, fishing, forestry or mining) and manufactured products. By and large services were not traded internationally. The Internet brought to our attention that there are tradable services as call centers and software manufacturing moved to India and other nations. It seems to me that we might consider tradable versus non-tradable as categories that apply to primary, secondary and tertiary industries.

We don't know how to export a lot of tropical fruits into international markets, and I would suppose that other primary products are not tradable. For example, clay and gravel might have such high transportation costs that they have to be produced close to where they are used. So too, some products harvested from the oceans and the forests may have only local markets.

So too, some manufactured products probably are not suitable for international commerce. I recently saw a factory that was producing shredded lettuce for fast food restaurants; I would not assume that one could export such a product.

I would note that while there is concern for the export of U.S. jobs by the import of services, such as call center services, we also export services. There are more than 600,000 foreign students in U.S. universities, and increasingly our educational institutions are offering Internet mediated educational services abroad. So too, our financial service industries offer services abroad. I wonder how much of the business of Amazon and eBay is in commerce of foreign buyers purchasing goods "retail" from the United States.

I suppose one lesson here is that the contents of the categories "tradable" and "not tradable" are changing rapidly. Another lesson is that popular ideas can be quite inaccurate if they don't keep up with the changes of the economy. A third lesson might be that our trade policy should be forward looking, considering markets that may soon develop for our exports and threats that may develop from new imports penetrating our domestic markets.