The above link goes to a short summary of the report which, in turn, links to the full report. So here I’ll just give an even shorter summary that I provided for the new impact page of the Royal Holloway Department of Economics:
Drone strikes are followed by strongly elevated rates of suicide attacks. On average, roughly one additional suicide attack occurred during a 30-day window following a drone strike in Pakistan. This suicide attack caused, on average, 20 deaths and 48 injuries. The trend of strike followed by suicide attack was elevated under Bush compared to Obama.
We don’t imagine that we’ve definitively settled this question and we cite some research that draws different conclusions (and explain why we don’t think they have settled the issue either). We will definitely return to this subject.