It means that national economies rely on international trade in overall economic activity . World trade expand faster than world output in the last 50 years by a significant margin.
Reasons:
Technological Change
Technological innovation led to the increase of productivity, and the advances in transport technology brought people and enterprises closer together so that the boundary of tradable goods and services has been greatly extended.
Continuing liberalization of trade and investment
It led to more and more companies to globalize production structure through investment abroad.