Control of corruption during each prime minister's tenure

Every prime minister since 1991, ranked by how the control of corruption 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	Helen Clark	10 Dec 1999 – 19 Nov 2008 from 2000	−0.5 points 2000 → 2008	−0.1 points/yr
2	John Key	19 Nov 2008 – 12 Dec 2016	−1.0 points 2008 → 2016	−0.1 points/yr
3	Jacinda Ardern	26 Oct 2017 – 25 Jan 2023	−1.7 points 2017 → 2022	−0.3 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_CC.SC): perceptions of public power used for private gain, petty and grand, a score from 0 to 100 with its 90 % interval · New Zealand data · as of Jul 2026.