Bloomberg reports: It’s no secret that Iran provides critical support to Syrian President Bashar al-Assad. The trouble comes in trying to figure out how much Iran spends and what that support actually looks like.

Estimates of Iran’s largesse vary considerably depending on who you ask, as my Bloomberg View colleague Eli Lake reported earlier this month. The United Nations’ special envoy for Syria, Staffan de Mistura, believes Iran spends about $6 billion annually propping up the Assad regime. Others believe that when you factor in Iran’s support for Hezbollah, which provides fighters to Assad, the number gets closer to $15 billion or $20 billion a year.

No matter the monetary total, a key component of Iran’s support for Assad is crude oil shipments. Syria once had a surplus of crude and even exported small amounts from its oil fields in the east. The civil war that broke out in 2011 has ravaged Syria’s crude production, which fell from about 400,000 barrels a day to roughly 20,000 barrels, according to recent estimates from the U.S. Department of Energy. [Continue reading…]