School choice under partial fairness

We generalize the school choice problem by defining a notion of allowable priority violations. In this setting, a weak axiom of stability (partial stability) allows only certain priority violations. We introduce a class of algorithms called the student exchange under partial fairness (SEPF). Each member of this class gives a partially stable matching that is not Pareto dominated by another partially stable matching (i.e., constrained efficient in the class of partially stable matchings). Moreover, any constrained efficient matching that Pareto improves upon a partially stable matching can be obtained via an algorithm within the SEPF class. We characterize the unique algorithm in the SEPF class that satisfies a desirable incentive property. The extension of the model to an environment with weak priorities enables us to provide a characterization result that proves the counterpart of the main result in Erdil and Ergin (2008).

Tactical Innovation, Democratic Governance, and Mixed Motives: Popular Movement Resilience in Peru and Ecuador

Urban popular movements that organize illegal land invasion communities present an intriguing puzzle. When most invasion organizations acquire land titles, their participation levels plummet and their agendas stagnate; yet some neighborhoods achieve land titles, sustain high participation, and acquire other services, such as piped-in water. Why do these organizations achieve movement resilience? The more typical trajectory of movement collapse is explained by the disappearance of the key selective incentive, property security. Some organizations, however, evade this “security trap” through mixed motives: their basic material agenda is supplemented by a nonmaterial and often altruistic agenda, which sustains participation in the face of reduced selective incentives. Examining three neighborhood case studies in Lima and Quito, this article argues that a new, “innovator” type of invasion organization is more likely to exhibit sustained participation and movement resilience due to tactical innovation, democratic governance, and mixed motives.