New Zealand abridged period life table from 2013–15 onwards

The New Zealand abridged life tables are derived every year for a 3-year time period. They provide an indication of trends in life expectancy and the mortality and survival experience at selected ages, until the complete period life tables are available. In 2016, we adopted a new statistical model to construct the abridged period life tables 2013–15. This model derives measures of mortality and life expectancy consistently across all population groups. This new statistical model was firstly developed and implemented to produce the New Zealand complete period life tables 2012–14 in 2015. See New Zealand period life tables: Methodology for 2012–14 for more detailed information on the new method. The data used to construct the abridged period life tables from 2013–15 three year period: Deaths registered in New Zealand, of people resident in New Zealand in the December years for the most recent three year period, respectively, by age groups (0, 1–4, 5–9, 10–15, ..., 80–84, 85 and over) and sex. The estimated resident population of New Zealand at 30 June of the mid year of the most recent three year period, respectively, by age groups (0, 1–4, 5–9, 10–15, ..., 80–84, 85 and over) and sex. Deaths numerator The period life tables were compiled from deaths registered, rather than deaths occurring, in each respective three-year period. Most death statistics refer to registrations rather than occurrences for a given time period, because there is generally a time lag between when the death occurred and when it is registered. The number of death registrations can be confirmed before the number of death occurrences for a given time period. 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. Population denominator (population-at-risk) The population estimates use the most recently available census data as a base (e.g. 2013 census). The estimated resident population is updated regularly for population change due to births, deaths, and net migration (arrivals less departures) of residents. Derived rates The period life tables were based on deaths averaged over three years. This is designed to reduce the impact of year-to-year statistical variations, particularly at younger ages where there may be a small number of deaths and at very old ages where the population at risk may be small. For some ages the subnational data does not enable death rates to be reliably estimated at all ages. Accuracy of the data Neonatal infant deaths Annual registration of neonatal (infants under four weeks of age) deaths may differ from the actual number of events in a given year, due to the lag between the date of death and the date of registration, and also under-registration. Neonatal deaths include very-low birth weight, extremely preterm, live births. A baby is born alive if the baby breathes or shows any other evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached. All live-born infants should be registered and counted as such, irrespective of length of gestation or whether alive or dead at the time of registration. If they die at any time following birth, they should also be registered and counted as deaths. Deaths The life tables are compiled from deaths registered, rather than deaths occurring, in each respective three-year period. Most death statistics refer to registrations rather than occurrences for a given time period, because there is generally a time lag between when the death occurred and when it is registered. For this reason, the number of death registrations can be determined before the number of death occurrences for a given time period. 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. Population estimates National population estimates are produced using a component methodology, where the base population is updated for the components of population change (births, deaths, and net migration). All population estimates have some uncertainty. Generally, the uncertainty associated with population estimates increases as the estimates move further away from the base (starting point). Uncertainty also increases as population estimates are disaggregated (eg by age or subnationally). The period life tables are based on deaths averaged over three years. This is designed to reduce the impact of year-to-year statistical variations, particularly at younger ages, where there may be a small number of deaths, and at very old ages where the population at risk may be small. Measures of uncertainty The statistical approach for estimating period death rates offers an explicit way of including uncertainty in the data and the parameters of the chosen model. The 50th percentile (median), 2.5th percentile, and 97.5th percentile estimates of the death rate and other life table variables are available at the detailed demographic level. Under the model, 95 percent credible intervals include the true underlying value 95 percent of the time. For example, 95 percent of the time life expectancy at birth for males is between 79.7 and 79.9 years. There is only a 2.5 percent chance that the true value is lower than 79.7 years, and a 2.5 percent chance it is higher than 79.9 years. en-NZ