Definition
Pareto optimality: an allocation of resources in which no one can be made better off without making at least one other person worse off.
Pareto improvement: a reallocation that makes at least one person better off and no one worse off.
- Pareto optimality is the economist's benchmark for an efficient allocation of resources.
- At that point all gains from reallocating resources are exhausted.
- It is used to judge whether a market has allocated resources efficiently.
Key Idea
- While any Pareto improvement remains, resources are still being wasted.
- Pareto optimality judges efficiency only, never fairness.
Testing an Allocation
- Start from any allocation and look for a change that helps someone at no one's expense.
- If such a change exists, the allocation is not yet Pareto optimal.
- Keep making these changes until none is left, and the final point is Pareto optimal.
Example
- On eBay a buyer pays £30 for a used phone they value at £45, while the seller valued it at only £20.
- The buyer gains £15 of surplus and the seller £10, and no third party loses, so the original 'no-trade' position was not Pareto optimal → the trade is a Pareto improvement.
- Once every mutually beneficial trade has happened and no further swap helps anyone without harming another, the allocation is Pareto optimal.
Link to Markets
- A perfectly competitive market such as foreign exchange reaches a Pareto-optimal allocation, where price = marginal cost.
- Market failure moves the economy away from Pareto optimality, leaving further gains from trade unrealised.
- So Pareto optimality links efficiency to the wider study of market failure and intervention.
Efficiency, Not Fairness
- Pareto optimality tells us only whether the gains from reallocation are exhausted.
- It says nothing about whether the distribution of resources is fair or equitable.
- An allocation where one person owns almost everything can still be Pareto optimal, because taking from them to help others makes them worse off.
Example
- Suppose one household holds £100 of a fixed pot and another holds £0; any transfer to the second reduces the first's share, so the extreme split is already Pareto optimal.
- Most people would call that outcome efficient but not equitable, which is why governments pursue equity goals even in an efficient market.
Exam technique
- Define Pareto optimality precisely before you apply it to a market.
- Note that it judges efficiency and not equity when evaluating an allocation.
Common Mistake
- Do not treat a Pareto-optimal outcome as automatically fair.
- It only means no one can gain without another person losing.
Self review
- Define Pareto optimality.
- What is a Pareto improvement?
- Which market structure reaches a Pareto-optimal allocation?
- Why does Pareto optimality say nothing about fairness?
