In general, growth is going on. This means that countries are accumulating capital and new technologies, a process that will itself have a big effect on the distribution of income. Many other disturbances may play a part. In Latin America, for instance, countries have wrestled with high inflation, deep recessions and huge swings in foreign-capital flows. Any of these shocks could have influenced wages and overshadowed the direct impact of trade.
Trade raises the demand for skills.
Traditional trade theory makes two big assumptions-that both rich and poor countries use the same kind of technology, and that capital is internationally immobile. The question is how much it matters. By reducing its trade barriers, a country may be able to import more new capital equipment. This will bring new technology, which will raise the demand for higher-skilled workers to use it. Thus freer trade will raise the premium paid to skilled workers in a way not envisaged by Stolper-Samuelson.