The Taliban regained control of Afghanistan this week, leaving questions about the U.S. costs of the nearly 20 years of war.

Despite the United States spending $8 billion over the past 15 years to combat Afghanistan’s opium trade, the Taliban was still able to maintain the country's status as the world’s biggest illicit opiate supplier. The Washington Post noted in December 2019 that Afghan opium production had "skyrocketed" over the course of the war.

"The drug trade is simply too deeply embedded in the accumulation and survival strategies of the Taliban, the state, the militias currently being stood up to fight the Taliban, and the wider population," Jonathan Goodhand, a professor in Conflict and Development Studies at the University of London, wrote last week in The Conversation. "This will unfortunately drive the global heroin market, as well as feeding the growing drug problem within Afghanistan and neighbouring countries."

Opium poppy cultivation in Afghanistan surged 37% from 2019 to 2020, according to a report in April from the U.N. Office on Drug and Crime (UNODC).

When the value of drugs and local consumption is taken into account, along with imported precursor chemicals, the UNODC estimates Afghanistan’s illicit opium economy is worth $6.6 billion.

The Taliban is involved in all facets of opium production -- poppy planting, extraction and trafficking. According to a report from the Special Inspector General For Afghanistan, the Taliban was able to derive up to 60% of its income from the opium trade.

A NATO report showed that the Taliban earns $1.5 billion annually from Afghanistan’s opium trade and “the financial independence allows the militia group to self-fund its insurgency without the need for support from governments or citizens from other countries.”

Afghanistan is estimated to have 80% of the world’s opium.