Pareto Optimality

Pareto optimality (also Pareto efficiency) is a state of a system in which no reallocation of resources can make any participant better off without making at least one participant worse off. Named for welfare economist Vilfredo Pareto, the criterion is the gold standard of efficiency assessment in economics — and also its most revealing limitation. A distribution in which one person owns everything and everyone else owns nothing can be Pareto optimal, if taking anything from the owner makes the owner worse off. Pareto optimality is therefore silent on distributive justice: it evaluates allocative efficiency without reference to how those allocations were achieved or whether they are equitable. Market Failure analysis uses Pareto optimality as its baseline: a market fails when it produces a Pareto-suboptimal allocation — one from which there exist mutually beneficial moves the market does not make. The concept is powerful precisely because it sets a minimal bar: if we cannot even achieve Pareto optimality, we are leaving gains on the table that everyone agrees are gains. Whether Pareto-optimal distributions are good distributions is a question Pareto optimality is constitutively unable to answer.