  Reserve systems are used to accommodate multiple essential or
underrepresented groups in allocating indivisible scarce resources by creating
categories that prioritize their respective beneficiaries. Some applications
include the optimal allocation of vaccines, or assignment of minority students
to elite colleges in India. An allocation is called smart if it optimizes the
number of units distributed. Previous literature mostly assumed baseline
priorities, which impose significant interdependencies between the priority
ordering of different categories. It also assumes either everybody is eligible
for receiving a unit from any category, or only the beneficiaries are eligible.
The comprehensive Threshold Model we propose allows independent priority
orderings among categories and arbitrary beneficiary and eligibility
thresholds, enabling policymakers to avoid comparing incomparables in
affirmative action systems. We present a new smart reserve system that
optimizes two objectives simultaneously to allocate scarce resources. Our Smart
Pipeline Matching Mechanism achieves all desirable properties in the most
general domain possible. Our results apply to any resource allocation market,
but we focus our attention on the vaccine allocation problem.
