Kaldor–Hicks efficiency

Pareto improvements are a small subset of Kaldor-Hicks improvements.

Suggest that the entry's name is changed to Kaldor-Hicks criterion, see discussion.--203.214.15.223 (talk) 19:33, 29 March 2008 (UTC)

Kaldor-Hicks efficiency (named for Nicholas Kaldor and John Hicks) is a type of economic efficiency that captures some of the intuitive appeal of Pareto efficiency, while having less stringent criteria and therefore being applicable in more circumstances.

Under Pareto efficiency, an outcome is more efficient if at least one person is made better off and nobody is made worse off. This seems a reasonable way to determine whether an outcome is efficient or not. However, some believe that in practice it is almost impossible to make any large change such as an economic policy change without making at least one person worse off. Under ideal conditions, exchanges are Pareto efficient since individuals would not voluntarily enter into them unless they were mutually beneficial. (Not all exchanges are Pareto superior: an exchange would not be superior if external costs exist, as they often do. If the voluntary exchange led to negative externalities such as pollution that hurt a third party, it would not be Pareto superior.)

Using Kaldor-Hicks efficiency, an outcome is more efficient if those that are made better off could in theory compensate those that are made worse off and lead to a Pareto optimal outcome. Thus, a more efficient outcome can in fact leave some people worse off.

The key difference is the question of compensation. Kaldor-Hicks does not require compensation actually be paid, merely that the possibility for compensation exists, and thus does not necessarily make each party better off (or neutral). Pareto efficiency does require making each party better off (or at least no worse off).

While every "Pareto improvement" is a "Kaldor-Hicks improvement", most Kaldor-Hicks improvements are not Pareto improvements. This is because, as the graph above illustrates, the set of Pareto improvements is a subset of Kaldor-Hicks improvement, which also reflects the greater flexibility and applicability of the Kaldor-Hicks criteria relative to the Pareto criteria. For example, in a society with two people suppose initially Person A has $10 and Person B $100. Assume that some policy change or other shock results in a situation where Person A winds up with $20 and Person B with $99. This change is not Pareto improving since Person B is now worse off. But it does satisfy the Kaldor-Hicks criteria since Person A could theoretically pay Person B anywhere between 1 and 10 dollars to accept this alternative situation.

The Kaldor and Hicks methods are typically used as tests of Pareto efficiency rather than efficiency goals themselves. They are used to determine whether an activity is moving the economy towards Pareto efficiency. Any change usually makes some people better off while making others worse off, so these tests ask what would happen if the winners were to compensate the losers.

Using the "Kaldor criterion" an activity will contribute to Pareto optimality if the maximum amount the gainers are prepared to pay is greater than the minimum amount that the losers are prepared to accept.

Under the "Hicks criterion", an activity will contribute to Pareto optimality if the maximum amount the losers are prepared to offer to the gainers in order to prevent the change is less than the minimum amount the gainers are prepared to accept as a bribe to forgo the change. The Hicks compensation test is from the losers' point of view, while the Kaldor compensation test is from the gainers' point of view. After several technical problems with each separate criterion were discovered, they were combined into the Scitovsky criterion, more commonly known as the "Kaldor-Hicks criterion", which does not share the same flaws.

The Kaldor-Hicks criterion is widely applied in welfare economics and managerial economics. For example, it forms an underlying rationale for cost-benefit analysis. In cost-benefit analysis, a project (for example, a new airport) is evaluated by comparing the total costs, such as building costs and environmental costs, with the total benefits, such as airline profits and convenience for travelers. (However, as cost-benefit analysis may also assign different social welfare weights to different individuals, e.g. more to the poor, the compensation criterion is not always invoked by cost-benefit analysis.)

The project would typically be given the go-ahead if the benefits exceed the costs. This is effectively an application of the Kaldor-Hicks criterion, because it is equivalent to requiring that the benefits should be enough that those that benefit could in theory compensate those that have lost out. The criterion is used because it is argued that it is justifiable for society as a whole to make some worse off if this means a greater gain for others.

Criticisms

The most common criticism of the Kaldor-Hicks criterion is that it only takes into account the absolute level of income, but disregards its distribution.

A related problem is that any social welfare functions based on Kaldor-Hicks criteria are cardinal in nature, and therefore suffer from the aggregation problems associated with discrepancies between the marginal value of money of rich and poor people.

At a more technical level, various versions of the Kaldor-Hicks criteria lack desirable formal properties. For instance, Tibor Scitovsky demonstrated that the Kaldor criterion alone is not symmetric: it's possible to have a situation where an outcome A is an improvement (according to the Kaldor criterion) over outcome B, but B is also an improvement over A. The combined Kaldor-Hicks criterion does not have this problem, but it can be non-transitive (A may be an improvement over B, and B over C, but A may not be an improvement over C).[1]

References

• Economic Analysis of Law, Richard A. Posner. Seventh Edition. Wolters Kluwer. 2007.

See also

• Compensation principle
• Welfare economics
• Pareto efficiency