GIS files of the 2020 electorates are available for download in a variety of formats from Stats NZ.
You can compare the 2020 electorate boundaries with the 2014 and 2007 electorate boundaries and local council boundaries using the Stats NZ Geographic Boundary Viewer.
Electorate boundaries coincide with meshblock boundaries. Meshblocks are the smallest geographic units for a geographic area. Both general and Māori electorate boundaries are defined by aggregations of meshblocks. Meshblocks are maintained by Stats NZ.
Meshblocks, which aggregate to form electorates, are updated annually by Stats NZ. The 2020 electorate boundaries reflect a number of minor technical adjustments to meshblock boundaries not involving population i.e. to follow the correct line of a river or road. The adjustments are visible in a small number of land and coastal areas where electorate boundaries otherwise unchanged between 2014 and 2020 do not exactly align.
The population data used by the Representation Commission was calculated by the Government Statistician using results from the 2018 Census and Māori Electoral Option.
General and Māori electoral populations at meshblock level are also available at Stats NZ.
More information about the mathematics and methodology used to produce the electoral population data can also be found at Stats NZ.