#### Summary

The analysis of welfare economics is built around the concept of Pareto efficiency. However, this efficiency criterion does not always represent a satisfactory answer. In order to solve this problem, and to find a new way to establish which allocation is best, economists have been since searching for new criteria to make a more informed decision. In this Learning Path we learn about some of these criteria.**Pareto efficiency**

#### Compensation criteria:

- Definition
- Kaldor’s criterion
- Hicks’ criterion
- Scitovsky’s criterion
- Little’s criterion
- Samuelson’s criterion

#### Theory of the…

This *efficiency criterion* was developed by *Vilfredo Pareto* in his book “Manual of Political Economy”, 1906. An allocation of goods is Pareto optimal when there is no possibility of redistribution in a way where at least one individual would be better off while no other individual ends up worse off.

A definition can also be made in two steps:

-a change from situation A to B is a Pareto improvement if at least one individual is better off without making other individuals worse off;

-B is Pareto optimal if there is no possible Pareto improvement.

This can be easily understood using an *Edgeworth box*. Starting from point C, two Pareto improvements can be made:

-from C to D: individual 1 would increase its *utility*, since a further *indifference curve* would be reached, while individual 2 will remain with the same utility;

-from C to E: individual 2 would maintain its utility while individual 2 increases theirs.

Once we are at point either D or E, no further Pareto improvements can be made. Therefore, D and E are Pareto optimal.

Following the same steps for every indifference curve, we can say that every point in which indifference curves from different individuals are tangent is Pareto optimal. The curve that links these infinite Pareto optima is called the contract curve.

**Video – Edgeworth box:**