Poland has a three-tier administrative division since 1999. On the first level, Poland is divided into 16 voivodeships (Polish: województwa, singular – województwo). These are sub-divided in 380 counties (Polish: powiaty, singular – powiat), and these counties contain 2,477 municipalities, known as gminas (plural - gminy). The municipalities are grouped into four categories: Major changes to the framework (such as a restructuring of local administration or regulation of the duties and powers of the self-government) is only possible by law.