  In a binary-treatment instrumental variable framework, we define
supercompliers as the subpopulation whose treatment take-up positively responds
to eligibility and whose outcome positively responds to take-up. Supercompliers
are the only subpopulation to benefit from treatment eligibility and, hence,
are of great policy interest. Given a set of jointly testable assumptions and a
binary outcome, we can completely identify the characteristics of
supercompliers. Specifically, we require the standard assumptions from the
local average treatment effect literature along with an outcome monotonicity
assumption (i.e., treatment is weakly beneficial). We can estimate and conduct
inference on supercomplier characteristics using standard instrumental variable
regression.
