The FOX drama debuted on August 29, 2005 to solid ratings of over 10.5 million viewers and a healthy number of 18-49 viewers. Prison’s first season finished with an average audience of 12.1 million. The second season declined a bit with an average of 10.1 million viewers. Season three dropped further to 8.2 million and the current season has averaged just 6.1 million viewers.
Based on the year four numbers to date, many have suspected that this season would be the drama’s last. Prison was missing from the midseason schedule and the network said it wouldn’t return until at least Spring. A spin-off had been in the works in 2007 but, with Prison’s declining numbers, those plans were put on hold.