(I'm not linking to it because it's not worth linking to.)
As Adam Smith put it:
Nothing, however, can be more absurd than this whole doctrine of the balance of trade, upon which, not only these restraints, but almost all the other regulations of commerce are founded. When two places trade with one another, this doctrine supposes that, if the balance be even, neither of them either loses or gains; but if it leans in any degree to one side, that one of them loses and the other gains in proportion to its declension from the exact equilibrium. Both suppositions are false. A trade which is forced by means of bounties and monopolies may be and commonly is disadvantageous to the country in whose favour it is meant to be established, as I shall endeavour to show hereafter. But that trade which, without force or constraint, is naturally and regularly carried on between any two places is always advantageous . . . to both.For more see Donald Boudreaux's article here.