Could Islamic State's 'looting economy' face defeat?

I think ISIS will face massive problems this year which will soon begin to materialize," Eckart Woertz, a senior researcher at the Barcelona Centre for International Affairs (CIDOB) and Middle East specialist, told CNBC. "ISIS revenue base is not sustainable and we will see cracks appearing. I would suspect these to increase over the year and for ISIS to have economic problems over this year. Its economy is based on looting —which is great if you have geographic expansion -- but, if anything, ISIS is on the retreat and you can hardly continue this business model in territory you've already looted.