I can't believe how good this article by Yale's Peter Schott is. One of the best practical descriptions I have ever seen of how the principle of comparative advantage actually works – and he is talking about the US-China bilateral trading relationship. Here are two paragraphs from his conclusion to give you a taste:

Even though increased trade with China may cause developed countries to abandon the production of their less-sophisticated goods, production of more-sophisticated goods, or the research and design services associated with them, is always waiting to take its place. Indeed, as is often pointed out, the creative destruction associated with these reallocations should be encouraged: allowing countries to produce according to their comparative advantage enhances the efficiency of production and encourages the availability of a wider variety of products at lower prices to consumers in all countries, thereby raising standards of living.

The problem, of course, is that all workers do not benefit equally from the adjustments associated with trade liberalisation. In developed countries, low-skill workers are disproportionately likely to be dislocated from their jobs as firms move up the quality ladder, and they may also have the hardest time finding matches with new employers. But it is precisely such losses to workers, and not a concern with jobs, that should be the focus of trade policy. Temporarily shielding certain jobs from import competition merely postpones an inevitable adjustment that only becomes more painful the longer it is delayed. Instead, trade policy, like Denmark’s flexicurity program, should facilitate the ability of workers to find new employment when existing occupations disappear.

This is also a great summary of the labor/employment policy position held by a lot of free traders, including myself. While we spend a lot of time arguing about protectionist measures, somehow policy debates over worker adjustment programs get lost in the shuffle. Makes it easy for the protectionists to label free traders as heartless bastards who don't care about the working man.