Trade has been around forever. In fact, this sort of thing was the central dispute of the Nullification Crisis... 150 years prior. What changed int he 70's was the massive increase in taxes and regulations that utterly crippled American companies. Shortly after, China decided to move away from communism, as it turned out to be retarded. So all the companies, like water seeking its level, left the newly-communist USA and moved to the newly-free-market China.