economics Economics () is a behavioral science that studies the Production (economics), production, distribution (economics), distribution, and Consumption (economics), consumption of goods and services. Economics focuses on the behaviour and interac ...

, additive utility is a

cardinal utility In economics, a cardinal utility expresses not only which of two outcomes is preferred, but also the intensity of preferences, i.e. ''how much'' better or worse one outcome is compared to another. In consumer choice theory, economists originally ...

function with the

sigma additivity In mathematics, an additive set function is a function \mu mapping sets to numbers, with the property that its value on a union of two disjoint sets equals the sum of its values on these sets, namely, \mu(A \cup B) = \mu(A) + \mu(B). If this ad ...

property. Additivity (also called ''linearity'' or ''modularity'') means that "the whole is equal to the sum of its parts." That is, the utility of a set of items is the sum of the utilities of each item separately. Let

S

be a finite set of items. A cardinal utility function

u:2^S\to\R

, where

2^S

is the

power set In mathematics, the power set (or powerset) of a set is the set of all subsets of , including the empty set and itself. In axiomatic set theory (as developed, for example, in the ZFC axioms), the existence of the power set of any set is po ...

S

, is additive if for any

A, B\subseteq S

, :

u(A)+u(B)=u(A\cup B)+u(A\cap B).

It follows that for any

A\subseteq S

, :

u(A)=u(\emptyset)+\sum_\big(u(\)-u(\emptyset)\big).

An additive utility function is characteristic of

independent goods Independent goods are goods that have a zero cross elasticity of demand. Changes in the price of one good will have no effect on the demand for an independent good. Thus independent goods are neither complements nor substitutes. For example, ...

. For example, an apple and a hat are considered independent: the utility a person receives from having an apple is the same whether or not he has a hat, and vice versa. A typical utility function for this case is given at the right.

Notes

* As mentioned above, additivity is a property of cardinal utility functions. An analogous property of

ordinal utility In economics, an ordinal utility function is a function representing the preferences of an agent on an ordinal scale. Ordinal utility theory claims that it is only meaningful to ask which option is better than the other, but it is meaningless to as ...

functions is

weakly additive In fair division, a topic in economics, a preference relation is weakly additive if the following condition is met: : If A is preferred to B, and C is preferred to D (and the contents of A and C do not overlap) then A together with C is preferab ...

. * A utility function is additive

if and only if In logic and related fields such as mathematics and philosophy, "if and only if" (often shortened as "iff") is paraphrased by the biconditional, a logical connective between statements. The biconditional is true in two cases, where either bo ...

it is both

submodular In mathematics, a submodular set function (also known as a submodular function) is a set function that, informally, describes the relationship between a set of inputs and an output, where adding more of one input has a decreasing additional benefi ...

and

supermodular In mathematics, a supermodular function is a function on a lattice that, informally, has the property of being characterized by "increasing differences." Seen from the point of set functions, this can also be viewed as a relationship of "increasi ...

References

Utility function types {{econ-stub

Notes

See also

References