A U.S.-based analysis firm says the Islamic State (IS) militant group's income has dropped by about one-third in the past 15 months, describing the decline as a threat to its long-term rule over its self-proclaimed caliphate.
In a report released on April 18, IHS says revenue for the group fell to $56 million in March from $80 million a month in mid-2015.
It says daily oil production in IS-controlled areas went down to 21,000 barrels from 33,000 barrels over the same time frame as production facilities suffered damage from air strikes.
Meanwhile, IS militants have lost 22 percent of their territory in Syria and Iraq and now rule over 6 million instead of 9 million people -- meaning the tax base for the group has become smaller.
In consequence, they have introduced new taxes on such activities as installing satellite dishes or exiting cities.