Pareto argued that since it takes two consenting people to trade and people aren’t stupid, they would only engage in trades that were either win-win or at least win-no-lose, both of which raise the total welfare of the participants. These trades later came to be called Pareto superior trades, and Pareto contended that in free markets, people would keep trading until they had exhausted all the Pareto superior trades. At that point trading would stop since any further trades would make someone worse off, and the market would reach an equilibrium point that later economists called Pareto optimal.
