New Zealand Period Life Tables 2022–2024

New Zealand period life tables: Methodology for 2017–2019 has detailed information from input data to estimation models used to derive the life tables. Deaths numerator Data source: deaths registered in New Zealand in the December years 2022–2024, respectively, by date of death, date of birth, sex, ethnicity, and geographic area of usual residence. For infant deaths, data provided by Health New Zealand | Te Whatu Ora was used for 2022 and 2023, while Stats NZ deaths by occurrence data was used for 2024. The life tables were compiled from deaths registered (except for infant deaths), rather than deaths occurring. Most death statistics refer to registrations rather than occurrences for a given time period, because of the time lag between when the death occurred and when it is registered. Hence, for a given time period, the number of death registrations can be confirmed before the number of death occurrences. For periods of a year or more, the difference between registrations and occurrences is generally small, so death statistics referring to registrations are suitable for most purposes. In 2022–2024, around 114,300 deaths were registered in New Zealand, made up of 58,800 male and 55,500 female deaths. An allowance for ethnic non-response among deaths was also made. There was no response to the ethnicity question for about 2.4 percent of deaths in 1996–1997, 3.5 percent of deaths in 2000–2002, 4.9 percent of deaths in 2005–2007, 0.7 percent of deaths in 2010–2012, 0.2 percent of deaths in 2012–14, 0.1 percent of deaths in 2017–2019, and 0.3 percent of deaths in 2022–2024. Because deaths in the first year of life are skewed towards the early part of this age, infant death rates were calculated from more detailed data. This involved the division of the first year of life into more detailed ages. Death records with missing ethnicity response are imputed using a statistical approach based on records with observed ethnicity response. Read ‘Ethnicity non-response in deaths data’ below for more information. Population denominator (exposed-to-risk population) Usually the mean population for a period is used as the denominator to calculate death rates. However, mean population estimates are not available for all ethnic populations. To ensure consistency of method among all population subgroups, the estimated resident population at 30 June of the census year (the midpoint) was used. The impact of using ‘midpoint’ rather than ‘mean’ population estimates is generally insignificant. The estimated resident populations at 30 June 1996, 2001, 2006, 2013, 2018, and 2023 were based on the census usually resident population counts at 5 March 1996, 6 March 2001, 7 March 2006, 5 March 2013, 6 March 2018, and 7 March 2023 respectively, and adjusted for: non-response to the census ethnicity question (prior to the 2018 Census) net census undercount residents temporarily overseas on census night births, deaths and net migration between census night and 30 June of the census year reconciliation with demographic estimates at ages 0–4 years (0–9 for 2013, and 0–14 for 2018 and 2023). Note: All population estimates used in the 1995–1997 to 2022–2024 life tables have been derived using the same methodology (see https://datainfoplus.stats.govt.nz/item/nz.govt.stats/57468853-e913-43df-8cca-51b40bf558f0 for more information). In addition, the ethnicity question used in the 1996 Census is the same as that used in birth and death registration forms from September 1995. The use of population estimates based on the 1996 Census also allowed the adjustment ratios presented in Ajwani (2003) to be incorporated into the 1995–1997 life tables. Incorporation of ethnic dimension An ethnic dimension was introduced into the estimation of national ethnic life tables. Each ethnic model includes two categories (eg, Māori and non-Māori for the Māori life tables). This enhancement significantly improves estimates for smaller ethnic groups ─ such as Pacific and Asian populations ─ particularly in age groups with low death counts or small populations. The inclusion of ethnicity allows the model to borrow strength across groups, resulting in more robust and plausible estimates. Model specification The core model structure remains unchanged from the 2017–2019 period. Deaths are assumed to follow a Poisson distribution, Dxse ~ Poisson (θxseNxse) Where: Dxse: number of deaths at age x, sex s, and ethnic group e Nxse: population at risk of dying θxse: underlying death rate The log of death rates is modelled as: log θxse ~ N(ß0 + ßxage + ßssex + ßeethnic + ßxsage:sex + ßxeage:ethnic, σ2) This hierarchical structure enables the model to produce stable estimates even in cells with limited data, by leveraging patterns across the full dataset. The ethnic effect is modelled using the same framework previously applied to regional effects in the 2017–2019 life tables. en