For trade to occur, it must make both parties better off. This is a positive-sum game, not a zero-sum game, because both sides gain. However, this does not mean that everyone is better off. The costs and benefits of trade extend beyond the actual buyer and seller in the transaction. And, once third parties are included, it is clear that trade can create winners and
Trade should make both sides better off. This does not necessarily mean that both sides will actually be better off. Trade can create both a winner and a loser.