The Impact of Drone Warfare on Suicide Bombings in Pakistan

Some analysts argue that US drone strikes targeting militants in the North Waziristan (NW) region of the erstwhile Federally Administered Tribal Areas (FATA) of Pakistan reduce militant activity. Others argue that these CIA-led strikes increase this activity. Cause and effect are difficult to disentangle because common underlying factors may drive both forms of violence. We use weather to identify a positive and large causal effect of drone strikes in NW on suicide attacks nationwide in Pakistan. Specifically, we use cloud cover and precipitation data for the NW, plus a dummy variable for a specific drone base closure, to instrument for drone strikes in the NW between July 2008 and the end of 2016 and identify a casual effect on suicide bombings in the whole country during this period. The idea is that drone strikes, but not suicide bombings, rely on good weather and appropriate air bases for their feasibility and effectiveness. We find that each drone strike causes, on average, at least 1 suicide bombing within the subsequent month, usually within a radius of 0 to 400 kilometers from the strike point. Strikes that eliminate militants’ leadership provoke particularly large reactions. We characterize 27-33 percent of all suicide bombings from July 2008 through 2016 as reactions to drone strikes. These results are robust to a variety of alternative specifications and estimators.