Political stability during each prime minister's tenure

Every prime minister since 1991, ranked by how the political stability changed from their first day in office. Politare shows what happened during a tenure; it does not claim the office-holder caused it.

#	Prime minister	In office	Total	Per year	Chart
1	John Key	19 Nov 2008 – 12 Dec 2016	+4.5 points 2008 → 2016	+0.6 points/yr
2	Helen Clark	10 Dec 1999 – 19 Nov 2008 from 2000	−4.0 points 2000 → 2008	−0.5 points/yr
3	Jacinda Ardern	26 Oct 2017 – 25 Jan 2023	−4.5 points 2017 → 2022	−0.9 points/yr

Sorted by total, highest first. Every row is indexed to the last count complete before the first day in office ("from" marks a start that had to move because that count had no data, or because the period cut it); Levels are per cent changes, rates are differences in points; "per year" compounds levels and divides rates. Tenures with under 12 months, or under three observations, are left out. points, 0 to 100, higher is better · World Bank, Worldwide Governance Indicators (GOV_WGI_PV.SC): perceptions of the likelihood of political instability or politically motivated violence, terrorism included, a score from 0 to 100 with its 90 % interval · New Zealand data · as of Jul 2026.