Here is Adam Smith speculating in The Wealth of Nations on the dynamic nature of the British labor market if all tariffs and barriers to imports were removed. Surely, there would be mass unemployment and catastrophic disruption. Not so, says Smith. And he uses a very elegant natural experiment to make his case:
via Cafe Hayek: Sudden disruption.
In short, “free trade now” is an excellent plan, one that we stand only to gain from.