Amendment frequency in New Zealand health legislation: a 20-year stable trend with no post-consolidation change

Background Amendment frequency is a proxy for legislative responsiveness and a practical indicator of governance transaction costs. Whether health system consolidation changes those patterns has not been examined empirically in New Zealand health legislation. Methods We analysed 73 legislative versions of four core New Zealand health acts across 2007-2026, yielding 20 annual observations. Mann-Kendall trend testing with Theil-Sen slope assessed the long-run trend, and Mann-Whitney U compared amendment frequency before Pae Ora (2007-2021) and after Pae Ora (2022-2026). Bootstrap confidence intervals used 1,000 resamples. Act-level inter-amendment intervals were also examined. Results No significant long-run trend was detected (Mann-Kendall τ=+0.283, p=0.10; Sen’s slope +0.22 amendments/year). Post-Pae Ora amendment frequency (mean 4.8/year) was not significantly different from pre-Pae Ora frequency (mean 3.0/year; Mann-Whitney U=22, p=0.19). Amendment activity differed by act: the HDC Act 1994 was most amended overall, the HSWA 2015 showed the shortest mean inter-amendment interval, and the MH Act 1992 showed the longest. The post-Pae Ora increase is most consistent with implementation-burst dynamics rather than a durable structural shift. Conclusions The Pae Ora 2022 consolidation neither reduced nor increased annual amendment activity within the first five post-consolidation years. Policymakers should not assume that structural consolidation lowers ongoing legislative maintenance burden without direct evidence.