“The proponents of quotas say, ‘Free trade is fine in theory but it must be reciprocal. We cannot open our markets to foreign products if foreigners close their markets to us,’” prominent economist Milton Friedman objected in the 1970s to the sort of arguments made by Trump, decades before the current president raised them. “The argument sounds reasonable. It is, in fact, utter nonsense. Exports are the cost of trade, imports the return from trade, not the other way around.”