An inadmissible rule is not preferred (except for reasons of simplicity or computational efficiency), since by definition there is some other rule that will achieve equal or lower risk for "all" formula_20. But just because a rule formula_19 is admissible does not mean it is a good rule to use. Being admissible means there is no other single rule that is "always" as good or better – but other admissible rules might achieve lower risk for most formula_20 that occur in practice. (The Bayes risk discussed below is a way of explicitly considering which formula_20 occur in practice.)