"Labour within immigration detention is not a widely acknowledged phenomenon, yet thousands of hours of work are being undertaken in detention centres throughout the world. In 2014, for example, over 495,000 hours-worth of work were undertaken by detainees in immigration detention centres in the UK alone. In 2015, this rose to over 923,000 hours-worth of work, and in 2016 over 537,000 hours-worth of work were undertaken between January and July 2016 (FOI request)."
See: The Immigration Industrial Complex: A global perspective on ‘unfree labour’ in immigration detention (Futures of Work, link):
“Taking a global perspective on this type of work is important as common colonial histories and global transfers in capital help to make sense of why detention practices are growing in popularity, and why migrants from particular countries of origin continue to be subjected to exploitative and ‘unfree’ labour at the hands of state parties and private corporations.”