Explanation

Angola withdrew its membership from OPEC on January 1, 2024: 

Angola: Joined OPEC in 2007 and announced its withdrawal in 2023 

Other countries that have withdrawn from OPEC:

Qatar: Terminated its membership in January 2019 to focus on natural gas production 

Ecuador: Suspended its membership in 1992, reactivated it in 2007, and withdrew in 2020 

Indonesia: Suspended its membership in 2009, reactivated it in 2016, and suspended it again that year