2 | Background – Immigration detention in Australia 2.1 Number of people in detention The number of people in closed immigration detention has reduced dramatically over the last decade. The number of people in detention peaked at over 10,000 in July 2013, before declining to fewer than 2,000 in early 2015.14 This reduction was largely due to the release of large numbers of asylum seekers from closed detention into alternative community arrangements; and a decrease in the number of people entering detention following a significant decline in boat arrivals to Australia. As of 31 December 2023, there were 872 people in detention. This comprised 824 men and 48 women.15 2.2 Length of detention The Commission acknowledges that the average period in closed detention has continued to decline during 2023. As of 31 January 2023, the average period in detention reached 806 days – which is the highest ever recorded.16 By 30 December 2023, the average period in detention had reduced to 625 days.17 12 This is still, however, far higher than in comparable jurisdictions. For example, in Canada the average length of detention was 15.7 days between 1 January and 31 March 2023.18 In the United Kingdom in 2022, 48% of all people who left immigration detention had been detained for 7 days or fewer.19 The negative impacts of prolonged detention are substantial, with the following observations previously made by the Commission:20 Prolonged closed detention is a risk factor for mental ill-health, as the negative impacts of immigration detention on mental health tend to worsen as the length of detention increases.21 This is of particular concern in the current context, given the consistently high average length of detention in recent years, and the large number of people being held in closed detention facilities for prolonged periods.