  This paper characterizes point identification results of the local average
treatment effect (LATE) using two imperfect instruments. The classical approach
(Imbens and Angrist (1994)) establishes the identification of LATE via an
instrument that satisfies exclusion, monotonicity, and independence. However,
it may be challenging to find a single instrument that satisfies all these
assumptions simultaneously. My paper uses two instruments but imposes weaker
assumptions on both instruments. The first instrument is allowed to violate the
exclusion restriction and the second instrument does not need to satisfy
monotonicity. Therefore, the first instrument can affect the outcome via both
direct effects and a shift in the treatment status. The direct effects can be
identified via exogenous variation in the second instrument and therefore the
local average treatment effect is identified. An estimator is proposed, and
using Monte Carlo simulations, it is shown to perform more robustly than the
instrumental variable estimand.
