TERRORISM is increasing. According to the Global Terrorism Database at the University of Maryland, groups connected with Al Qaeda and the Islamic State committed close to 200 attacks per year between 2007 and 2010, a number that grew by more than 200 percent, to about 600 attacks, in 2013. Since 9/11, the study of terrorism has also increased. Now, you might think that more study would lead to more effective antiterrorism policies and thus to less terrorism. But on the face of it, this does not seem to be happening. What has gone wrong?…