How many people does Immigration detain, and for how long? Efforts to gain this information under the OIA have been unsuccessful; however the Department of Labour's annual reports track detentions as a performance indicator. Here's what I've dug out of them since 2003, when the current regime began:
| 2003 | 2004 | 2005 | 2006 | |
| Auckland Central Remand Prison | 15 | 26 | 14 | 13 |
| Mangere "Accomodation" Centre | 131 | 84 | 62 | 57 |
| Released on conditions | N/A | 66 | N/A | 40 |
It's unclear how much double-counting there is here - whether for example someone detained in 2004 under a warrant of commitment counts only in that year, or in subsequent years as well, but its still more information than we had previously.
By way of comparison, as at 23 May 2007 [PDF], Immigration had 26 people in custody with Corrections, split between the Auckland Central Remand, Waikeria and Rimutuka prisons. Which suggests a rather dramatic increase in the use of detention.