ISIS may have lost a lot of its income in 2016 thanks to coalition efforts to cripple its revenue streams.
U.S. counterterrorism officials say ISIS is struggling to pay its fighters after airstrikes destroyed more than 1,200 ISIS oil tanker trucks over the past 15 months.
The U.S. and Iraq also targeted Middle Eastern money-changing services that allow the terrorist organization to make purchases or pay its operatives. But experts say ISIS can change how it makes money.
Matthew Levitt from the Washington Institute for Near East Policy told CNN: "Think of it as squeezing a balloon, not hard enough to pop it, but hard enough to squeeze it. If you squeeze it here, it's going to expand someplace else. We have seen in the past, and we can expect to see now, they will expand into other directions."
One of those directions is antiquities. ISIS already sells artifacts looted from areas it controls. It's released videos of buildings and statues being smashed, but other antiquities like coins or artwork can be sold on the black market for thousands of dollars.
ISIS also makes hundreds of millions of dollars in tax revenue. Once it takes over a territory, it taxes residents on everything from crops to medicine to bank transactions.
Even though ISIS is losing some of its revenue streams, that might not decrease its ability to carry out terrorist attacks, since they're relatively inexpensive to finance.
A Middle Eastern official told The Washington Post: "Yes, we're hurting them financially. But I'm not yet seeing such impacts on their covert activities."
Correction: A previous version of this story misidentified the name of the expert from the Washington Institute for Near East Policy as Michael Levitt. The correct name is Matthew Levitt.