Object Allocation via Immediate-Acceptance: Characterizations and an Affirmative Action Application

Which mechanism to use to allocate school seats to students still remains a question of hot debate. Meanwhile, immediate acceptance mechanisms remain popular in many school districts. We formalize desirable properties of mechanisms when respecting the relative rank of a school among the students' preferences is crucial. We show that those properties, together with well-known desirable resource allocation properties, characterize immediate acceptance mechanisms. Moreover, we show that replacing one of the properties, consistency, with a weaker property, non-bossiness, leads to a characterization of a much larger class of mechanisms, which we call choice-based immediate acceptance mechanisms. It turns out that certain objectives that are not achievable with immediate acceptance mechanisms, such as affirmative action, can be achieved with a choice-based immediate acceptance mechanism.