The enrolment gap: who is not enrolling with primary health organizations in Aotearoa New Zealand and what are the implications? An exploration of 2015–2019 administrative data

BACKGROUND: Primary Health Care (PHC) is the entry point to accessing health services in many countries. Having a high proportion of the population enrolled with a PHC provider is key to ensuring PHC fulfils this role and that it contributes to achieving better equity in health. We aimed to understand the extent to which people in Aotearoa New Zealand are enrolling with Primary Health Organizations (PHOs), how enrolment rates have evolved over time, and variations across District Health Boards (DHBs) and socio-demographic groups. METHODS: We analysed administrative data on the proportion of people enrolled in PHOs and breakdowns across DHBs, and by age, ethnicity and deprivation, for the years 2015–2019. RESULTS: About 6% of the population was not enrolled in 2019. There are persistent differences across socio-demographic groups as well as geographically. Māori have lower enrolment rates than New Zealand European/Other groups. Young people (15–24 years) are the least likely to be enrolled. The most affluent areas have the highest enrolment rates. Auckland DHB shows the lowest enrolment rates. CONCLUSIONS: Enrolments remain below full population coverage and inequities exist between socio-demographic and geographic groups. Potential reasons explaining these trends include methodological limitations as well as real issues in accessing services. We recommend (a) work towards minimising data issues in relation to this indicator to improve its accuracy and value in signalling trends in access to PHC services, and (b) investigating the reasons for the potential widening of the inequities identified, in particular issues preventing Māori and younger people from enrolling. This study deepens our understanding of enrolment rates as an indicator for tracking equity in PHC. Other countries can learn from the Aotearoa New Zealand case to draw lessons for improving equity in health care. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12939-021-01423-4.