  The estimation of the causal effect of an endogenous treatment based on an
instrumental variable (IV) is often complicated by attrition, sample selection,
or non-response in the outcome of interest. To tackle the latter problem, the
latent ignorability (LI) assumption imposes that attrition/sample selection is
independent of the outcome conditional on the treatment compliance type (i.e.
how the treatment behaves as a function of the instrument), the instrument, and
possibly further observed covariates. As a word of caution, this note formally
discusses the strong behavioral implications of LI in rather standard IV
models. We also provide an empirical illustration based on the Job Corps
experimental study, in which the sensitivity of the estimated program effect to
LI and alternative assumptions about outcome attrition is investigated.
