Variously referred to as a country, province, or region, Northern Ireland is a portion of the United Kingdom located in the northeast of the island of Ireland. The Republic of Ireland and Northern Ireland have an open border to the south and west of each other. Its population, as of the 2021 census, was 1,903,175, or around 3% of the population of the United Kingdom and 27% of the island of Ireland. Certain devolved policy topics are under the purview of the Northern Ireland Assembly, which was instituted by the Northern Ireland Act 1998. The UK Government retains jurisdiction over other matters. Under the principles of the Belfast Agreement, the governments of Northern Ireland and Ireland collaborate in a number of sectors.