In addition, the researchers found, there has been a striking shift away from publications and social media portraying a functioning state with competent bureaucrats, thriving businesses and happy citizens. The Islamic State, also called ISIS and ISIL, claims that it is building a new caliphate — or unified Muslim land — a claim that has become increasingly threadbare.

“It’s not just the numeric decline,” said Daniel Milton, director of research at the Combating Terrorism Center at West Point and the author of the new report. “The caliphate was their big selling point. Now there’s an inability to say we’re doing the things that make us a state. And that was behind their broad appeal.”

At the peak of the Islamic State’s media output, in August 2015, the group released more than 700 items from official outlets in Syria and several other countries. During the month of August 2016, after a year of airstrikes and other assaults, that number had declined to under 200, according to the study.