is known for its definitive and numerous lists on wealth, such as Top-Earning Dead Celebrities and World's Most Innovative Companies. After reports surfaced this week about how al-Shabaab earns its money
, we realized that Forbes had missed a list: World's Wealthiest Terrorist Organizations. To help us put it together, Day 6 spoke to Bill Tupman
, a research fellow at the University of Exeter who specializes in transnational crime and has written about terrorist financing.