A protectionist strategy
employed by some (primarily developing
) nations to help foster
the growth of local industries
Let's say a country's populace enjoys the benefits of, say, refrigerators. However, there are no domestic fridge manufacturers, meaning that all iceboxes must be imported from abroad. In this case, a country may take steps to encourage the founding of local refrigerator companies through tax or other incentives and simultaneously establish tariffs on imports of foreign refrigerators. In this way, the new domestic firms are given a fighting chance to grow instead of being forced to compete with potentially much larger and more mature foreign corporations.
There are several downsides to this strategy, of course. First, the products produced by smaller, local companies are likely to be more expensive and of lower quality than comparable imported models, thus putting the bulk of the economic strain on the consumers. Second, foreign governments may choose to respond to an import substitution regime with tariffs of their own, and these could stifle the growth of domestic exporters. Since this second point may not come into play until the domestic economy has grown in strength, import substitution is generally employed by countries with little or no export sector. A notable exception to this pattern is India, which has worked at import substitution for some time despite their maturing status.
While I am personally not very convinced of the long-term merits of import substitution, I do think that themusic is right when he points out that it is always the dominant trading powers that tend to favor free trade. This was as true of Britain in the 19th century as of today's US. Ain't that always the way?