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TOPIC:
OPTIMAL DYNAMIC TREATMENT REGIMES WITH IMPERFECT COMPLIANCE
ABSTRACT
Dynamic treatment regimes are treatment assignments tailored to heterogeneous individuals’ needs. In a dynamic regime, each period’s assignment rule maps past outcomes and treatments onto a current allocation decision. The optimal dynamic treatment regime is a sequence of assignment rules that maximizes average welfares. This paper considers identification of optimal dynamic regimes when observed outcomes and treatments are generated from multi-period experiments in the presence of non-compliance, or more generally from observational studies. The biostatistics literature that studies optimal treatment regimes relies on the sequential randomization assumption, although non-compliance is prevalent especially in multi-period settings. This paper relaxes sequential randomization and proposes a simple nonparametric structural models, in which we can partially learn optimal dynamic regimes via exclusion restrictions. We first characterize the identified set of optimal regimes as a subset of all possible regimes, and calculate resulting bounds on the optimal welfares and regrets. We then show how additional variation in exogenous variables helps shrink the identified set of the objects of interest. In the paper, we also discuss the cardinality reduction of the set of possible regimes for computational, institutional, and practical reasons.