Understanding statistics

Understanding violence statistics

In Aotearoa New Zealand there is no single source of data for identifying and monitoring the many types of violence in our communities.  

There are two main sources of data available to researchers, policymakers, service providers and funders seeking to quantify and monitor family violence and sexual violence: population-based research and administrative data.  

Both population surveys and administrative data sets are likely to underestimate the true prevalence of violence occurring in our communities.

Population-based research  

Population-based research provides the most reliable source of prevalence data available, by providing a snapshot at a point of time. If the survey is repeated at another time, using the same questions and surveying a representative population, it may be possible to identify trends over time. Below are some examples of population-based research studies:

He Koiora Matapopore | 2019 NZ Family Violence Study is Aotearoa New Zealand’s most robust source of data for the lifetime prevalence of intimate partner violence and sexual violence for women and men. A comparable survey of women only was completed in 2003 – the New Zealand Violence Against Women Study (2003).

The Ministry of Justice has completed regular cycles of the New Zealand Crime and Victims Survey (NZCVS) since 2018. This survey replaced the New Zealand Crime and Safety Survey (NZCASS) which was conducted in 2006, 2009 and 2014. NZCVS provides prevalence data for interpersonal violence, including family violence and sexual violence in the past year. The survey also provides data on who experiences interpersonal violence and the proportion of incidents reported to the Police.  

The Youth2000 survey series surveying secondary school students is a valuable source of prevalence data for adolescents’ exposure to family violence and experiences of unwanted sexual experiences. This survey has been conducted regularly since 2001, most recently in 2019.  

Longitudinal studies follow a cohort of participants over a number of years. These studies can identify how past experiences influence peoples’ lifetime outcomes.  

The Dunedin Multidisciplinary Health and Development Study (The Dunedin Study) has followed around 1000 children born in Dunedin over one year in 1972-3. This study provides information on the long-term consequences of early childhood and adolescent experiences.

The Christchurch Health and Development Study commenced in 1977.

Growing Up in New Zealand is following more than 6,000 New Zealand children until they turn at least 21. The children were recruited in 2009 and 2010 in Auckland, Counties Manukau and Waikato District Health Board regions. The cohort represents the diversity of Aotearoa New Zealand’s population in the 21^st century.  

The Pacific Islands Families Study (PIF Study) is a longitudinal study following a cohort of 1398 Pacific children born in 2000.  

Administrative data sets

Administrative data sets are maintained by government agencies and service providers for monitoring resource use and for policy development and implementation. This statement remains true today:  

"... although there are some useful administrative data sets in New Zealand, none could currently be considered a reliable source of data for monitoring trends in family violence in the community over time." (Gulliver & Fanslow, 2013, p.78).

Administrative data sets (for example, from the Police, Oranga Tamariki, courts, hospitalisations, family violence and sexual violence services etc) reflect levels of service activity rather than the number of people who experience family violence or sexual violence in any community. According to the NZCVS only 24% of interpersonal violence is reported to police, and reporting varies by types of offences (just 6.6% of sexual assault offences are reported). Also, agencies tend to change their policies, procedures and how they record family violence over time. This can lead to changes in the numbers that don’t necessarily reflect increases or decreases in rates of violence. Similarly, it is not known how much differences in level of service activity are influenced by changes in willingness to report.

These papers describe the complexities associated with the collection and collation of family violence and sexual violence statistics in Aotearoa New Zealand:

Abuse of older people in Aotearoa New Zealand: An examination of potential data sources (Boven, N., Kolandai, K., Underwood, L., Malihi, A., & Milne, B., Ministry of Social Development, 2023).

Data collected about victims of serious crime (McGregor, K., Office of the Chief Victims Advisor, 2017).

Family violence indicators: Can administrative data sets be used to measure trends in family violence in New Zealand? (Gulliver, P., & Fanslow, J.L. Superu, a division of Families Commission, 2013).

Measurement of family violence at a population level: What might be needed to develop reliable and valid family violence indicators? Issues Paper 2. (Gulliver, P., & Fanslow, J.L. New Zealand Family Violence Clearinghouse, University of Auckland, 2012). 

Indigenous data sovereignty

The rapid growth of digital technologies has created a global explosion in the generation of data. In this increasingly digitised world, more data than ever is1 being collected, stored, linked, and shared. But who defines data? Who owns it? Who has access? And who benefits? The concepts of data sovereignty, Indigenous data sovereignty, and Māori data sovereignty were developed to help answer such complex and urgent questions.

For Indigenous Peoples, data sovereignty is integral to a wider discussion about autonomy and self-determination. Indigenous data sovereignty recognises that Indigenous Peoples have inherent rights to their own data.

This quote comes from the Introduction to Mana raraunga | Data sovereignty (p.4).

These resources explore the concept of Māori data sovereignty and the importance of data sovereignty for all indigenous peoples around the world.  

Mana raraunga: He aha tēnei, ā, he aha tōna pānga ki Aotearoa? | Data sovereignty: What is it and why does it matter in Aotearoa New Zealand? (Te Apārangi | Royal Society, 2023).

Indigenous statistics: From data deficits to data sovereignty (Andersen, Walter, Kukutai & Gabel, 2025).

Search the Vine library to learn more about Mana raraunga | Data sovereignty