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In fact, the US, Britain, and other countries are launching a series of air strikes in Syria in order to destroy one of the main ways ISIS gets its revenue - oil trucks and fields.
And you can see why Western forces are aiming at stopping the flow of funding - ISIS rakes in $80 million (£53 million) per month.
Around $1.1 million (£730,793) per day is made from just oil revenue alone.
Research house IHS unveiled the figures and also pointed out that the amount of revenue and the way it funds itself isn't like any other Islamist terrorist group out there. This is because while most, like Al Qaeda, relies on donations for funding its operations, ISIS is self-sufficient.
"Unlike al-Qaeda, the Islamic State has not been dependent on money from foreign donors, to avoid leaving it vulnerable to their influence," said Columb Strack, senior analyst at IHS in a report, cited by the Financial Times.
As colleague Oscar Williams-Grut reported yesterday, ISIS gets its funding from the following ways:
- Scamming banks
- Selling antiques and artifacts
- Ransoms
- Oil
- Taxation
- Donations
AFP reported that oil is believed to be making ISIS an estimated $50 million (£33 million) a month from this trade, equivalent to $600 million (£398 million) a year. However IHS pegs oil as worth 43% of total revenue.
And while campaigners and some politicians have questioned the government's insistence that bombing oil trucks and fields is the best way to stem ISIS funding, Strack said that air strikes are "paying off" because the bombing is destroying one of ISIS' main ways in funding itself.