Definition and Evaluation of the Monotonicity Condition for Preference-Based Instruments

摘要

BackgroundPreference-based instrumental variable methods are often used in comparative effectiveness research. Many instrumental variable studies estimate the local average treatment effect (i.e., the effect in the “compliers”) under the assumption of monotonicity, i.e., no “defiers,” and well-defined compliance types. However, the monotonicity assumption has not been empirically tested and the meaning of monotonicity itself is unclear.