Matthew M. Reed writes: The early estimate for ISIS oil revenues was $2-3 million a day. Media coverage ran with that number and so did U.S. officials for a time. However, the price/volume assumptions built into it were never clear. “It’s not an estimate that the U.S. intelligence community or the Pentagon is endorsing or has come up with,” a Pentagon spokesman said in September 2014.

The first official U.S. government estimate for ISIS oil revenue came in October last year. Then-Treasury Undersecretary David Cohen estimated that ISIS probably earned $1 million a day in June—before the anti-ISIS coalition intervened. That estimate held up until February 2015 when Cohen said ISIS revenues had fallen to just $2 million a week (or ~$300,000 a day). At that point, U.S. officials became convinced oil was not the top money maker for ISIS; instead the group relied more on taxation, tolls, ransom and theft. Official estimates came with big caveats but the U.S. government apparently believed it had cut down ISIS oil revenues by two-thirds.

That estimate lasted until July, when Treasury’s Assistant Secretary for Terrorist Financing Daniel Glaser concluded that oil ranked third among ISIS revenue streams, but it was still significant. “Earlier this year ISIL made about $40 million in one month, off of the sale of oil. So if you want to extrapolate that out, you get to about $500 million in the course of a year,” he said. $500 million a year works out to almost $1.4 million a day, which is almost a five-fold increase from the lowball claim made in February. (FT estimates revenue at $1.5 million a day as well.) [Continue reading…]

See also Part Two of this report.