Pareto Optimal

According to the modern version, commonly taught even in introductory economics, a competitive free-market equilibrium is “Pareto optimal.” That means that once such an economy is in equilibrium, it is impossible to improve the economic welfare of everyone. Any interference will make someone worse off. For graduate students, this conclusion is presented as a mathematical theorem of some elegance—elevating the notion of free-market optimality into a high scientific achievement.

Akerlof, George A.; Shiller, Robert J.. Phishing for Phools (p. 5). Princeton University Press.