Pareto Efficiency

Pareto efficiency means no feasible change can make someone better off without making anyone worse off, under the specified preferences and constraints. It differs from fairness and incentive equilibrium.

An allocation is Pareto efficient when no feasible alternative makes at least one person better off without making anyone worse off, under the specified preferences and constraints. A Pareto improvement is such a no-loss gain. Efficiency is therefore relative to the feasible set and whose outcomes are included.

The criterion does not rank all efficient allocations or settle fairness. A very unequal distribution can be efficient under particular assumptions, while an apparently settled outcome can remain inefficient if a mutually beneficial exchange exists. Nash equilibrium concerns unilateral incentives and is a different concept; equilibrium can be Pareto dominated.

When to use it

When analyzing data; when building predictive models; when evaluating statistical claims; when quantifying uncertainty.

How it can help

Define the affected people and feasible alternatives, look for mutually beneficial changes, and state the distributional questions that remain after avoidable losses are removed.