Impartial culture (IC) or the culture of indifference[1] is a probabilistic model used in social choice theory for analyzing ranked voting method rules.
[2][3] The model is understood to be unrealistic, and not a good representation of real-world voting behavior, however, it is useful for mathematical comparisons of voting methods under reproducible, worst-case scenarios.
[2] There are three variations of the model that use different subsets of the full set of possible rankings, so that different election permutations are drawn with different probabilities: This model assumes that each voter's ranking is randomly selected from a uniform distribution.
)[2] This reduces the set of possible elections by eliminating those that are equivalent if the voter identities are unknown.
[2][8] For example, the two-candidate, three-voter election {A>B, A>B, B>A} is equivalent to the election where the second and third voters swap votes: {A>B, B>A, A>B}, and so all variations on this set of votes are only included once.
The set of all such elections is called the anonymous equivalence class (AEC), and if the strict rankings are being chosen by
[2] This is also referred to as the "Dirichlet" or "simplex" model.
[9][10][11] This reduces the set of possible elections further, by eliminating those that are equivalent if the candidate identities are unknown.