Sorin Cosoveanu writes that 27 postes administratifs (administrative stations) have been elevated to departments. They are Aderbissanat, Iférouane, and Ingall in Agadez region; Bosso, Goudoumaria, and N’Gourti in Diffa region; Dioundou, Falmèye, and Tibiri in Dosso region; Bermo, and Gazaoua in Maradi region; Bagaroua, Malbaza, Tassara, and Tillia in Tahoua region; Abala, Ayérou, Balléyara, Bankilaré, Banibangou, Gothèye, and Torodi in Tillabéry region; and Belbédji, Damagaram Takaya, Dungass, Takiéta, and Tesker in Zinder region. They were defined by a law of 2011-08-01, and came into effect with the appointments of prefects on 2012-02-29. Source [4] confirms this.

Niger is divided into seven régions (regions) and one communauté urbaine (urban commune). Before this change, the regions were further subdivided into the 36 départements (departments) shown here.

Change history:

1. 1964-11-05: Law No. 64-039 created 32 arrondissements.
2. 1969-04-10: Law No. 69-29 created Arlit arrondissement in Agadez department.
3. 1972-02-17: Law No. 72-03 replaced Maradi arrondissement by Aguié, Guidan-Roumdji, and Madarounfa arrondissements in Maradi department.
4. 1992: Tillabéri department formed by taking all arrondissements except Niamey out of Niamey department.
5. 1998: Name of Matamèye arrondissement changed to Kantché.
6. 2001-08-10: Law No. 2001-023 changed the status of departments to regions and arrondissements to departments.
7. ~2002: Kollo department created in Tillabéri region. Abalak department split from Tchin-Tabaraden in Tahoua region. Name of Agadez department changed to Tchirozérine.

Other names of subdivisions: 

1. Kantché: Matamèye (obsolete)
2. Mirriah: Miriah, Mirria (variant)
3. Tchirozérine: Agadez (obsolete); Tchérozérine (variant)
4. Tillabéri: Tillabéry (variant)

Sources:

1. [1] Institut National de Statistique - Niger  website has population projections for 2010, found by going to the individual region pages in the right-hand sidebar (retrieved 2012-08-21). The projections for the departments within a given region are equal to the 2001 census population times a constant factor, which is different for each region. For example, the ratio between the 2010 projection and the 2001 census for each of the eight departments in Tahoua region is 1.347422±0.000004; for the three departments in Agadez, it's 1.515097±0.000008. This is surely a clue as to how the projections were made.
2. [2] 2001 census data are from the Institut National de Statistique - Niger  website (retrieved 2009-06-05).
3. [3] Répartition de la Population du Niger par Sexe selon la Région et le Département  has 2001 census data, also showing Abalak, and gives areas of departments (retrieved 2012-08-21).
4. [3] DirectNiger.com : "Conseil des ministres: le gouvernement adopte plusieurs projets de textes et des mesures nominatives" (retrieved 2012-08-22).