  In many situations, researchers are interested in identifying dynamic effects
of an irreversible treatment with a static binary instrumental variable (IV).
For example, in evaluations of dynamic effects of training programs, with a
single lottery determining eligibility. A common approach in these situations
is to report per-period IV estimates. Under a dynamic extension of standard IV
assumptions, we show that such IV estimators identify a weighted sum of
treatment effects for different latent groups and treatment exposures. However,
there is possibility of negative weights. We consider point and partial
identification of dynamic treatment effects in this setting under different
sets of assumptions.
