when there may exist heterogeneous treatment effects across groups, the late is unlikely to be equivalent to the ate. in one example, angrist (1989) attempts to estimate the causal effect of serving in the military on earnings, using the draft lottery as an instrument. the compliers are those who were induced by the draft lottery to serve in the military. if the research interest is on how to compensate those involuntarily taxed by the draft, late would be useful, since the research targets compliers. however, if researchers are concerned about a more universal draft for future interpretation, then the ate would be more important (imbens 2009).