HHI trends

Report notes

1. Retail reports are released after the 10th business day of each month. The next scheduled release is due on 17/04/2026. The reports are built off a live system and the data is subject to change as registry events are processed (e.g. backdated corrections or withdrawn switches).

2. The Herfindahl-Hirschman index (HHI) is a measure of market concentration. This metric is derived from parent company share of ICPs for the market segment selected in each regional market where retailers operate and compete. The regional markets are represented by the pricing regions or network reporting regions. The HHI presented for other region types is the connection weighted average of the HHI for the network reporting regions.

3. Market segment breakdowns are available from September 2013 when ANZSIC codes were introduced into the registry in a field maintained by the trader. No breakdown is available at NSP level. Market segments are not mutually exclusive. Residential connections have no ANZSIC code. Small and Medium Enterprise (SME) connections are defined as those assigned meter categories 1 and 2 (low voltage up to 500A) with an ANZSIC code excluding those relating to central or local government and other utility services. Industrial connections have ANZSIC codes from A through E while commercial connections use ANZSIC codes F through Z. More information on ANZSIC codes is available at www.stats.govt.nz.

4. Region types are either network based or derived from standard statistical boundaries. Network-based regions are network supply points (NSPs), network reporting regions, and zones. Mappings are available in the NSP table which is available as a wholesale report. Other regions are derived from ICP location data and statistical boundaries (2013 census). ICPs without location data default to the location of their NSP. Main centres use Territorial Authority boundaries (City Councils) where Wellington includes Porirua City, Upper Hutt City, Lower Hutt City, and Wellington City. Many data reports allow for the selection ‘All regions’ (where the regions are not the data series) to get data for all regions in a single file. Regions are listed in a North to South ordering, except for NSPs which are listed alphabetically.