Main causes of death among children aged 4 and under in New Zealand

Year: Death registration year
Sex: Sex of person at death
Age-standardised rates: The rates in this file have been age standardised to take into account the differences in the age distribution of the population over time. MoH used direct age-standardisation and the WHO World Population as the standard population
Ethnic group: Unknowns are included in Non-Māori.

All cancer: All types of malignant neoplasms (ICD classification C00-C96 & D45-D47)
Ischaemic heart diseases: Also known as Coronary artery disease (CAD). Includes myocardial infarction, related complications, and other acute and chronic ischaemic heart diseases (ICD classification I20-I25)
Cerebrovascular diseases: Includes strokes and other cerebrovascular diseases (ICD classification I60-I69)
Chronic lower respiratory diseases: Includes bronchitis, asthma, emphysema etc (ICD classification J40-J47)
Other forms of heart disease: ICD classification I30-I52
Influenza and pneumonia: ICD classification J09-J18
Diabetes mellitus: includes Diabetes Type 1 and 2 (ICD classification E10-E14)
Motor vehicle crashes: Deaths that occurred in collision and non-collision events. The data provider used the term 'accidents', which we have rectified to 'crashes' to avoid ambiguity on the presumed responsibility of the events (ICD classification V , not all sub-categories are included)

https://www.health.govt.nz/nz-health-statistics/national-collections-and-surveys/collections/mortality-collection

This dataset includes deaths where COVID was coded as the underlying cause of death. These deaths are coded to the following ICD classification; Chapter 22 Codes for special purposes > U00–U49 Provisional assignment of new diseases of uncertain aetiology or emergency use > U07 Emergency use of U07. The 3-character code U07 can also include vaping-related deaths, though none were reported in 2020 or 2021.

Ethnic breakdowns of mortality data are only shown from 1996 onwards because there was a significant change in the way ethnicity was defined, and in the way ethnicity data was collected in 1995.
Rates of mortality were recalculated from 1996 to2018 to reflect ongoing updates to data in the Mortality Collection, (eg, following the release of coroners' findings) and the revision of population estimates from Stats NZ. Population data used to calculate the rate of mortality was derived from datasets downloaded from the Stats NZ website. Estimated resident population counts are regarded as the best available population, and are used whenever possible as the denominator to calculate the rate of mortality.

At URL provided, in 'Historical mortality (1948–2021)' tab, under 'Download the datasets' headline select 'Historical_mortality_Table.xlsx' file.

The Mortality Collection (MORT) classifies the underlying cause of death for all deaths registered in New Zealand, and all registerable stillbirths (fetal deaths).

The Mortality Collection was established to provide data on causes of death for New Zealand’s vital statistics, for public health research, policy formulation, monitoring the effectiveness of health programmes, and cancer survival studies. A dataset of each year’s mortality data is sent to the World Health Organization to be used in international comparisons of mortality statistics.

Data from 1948–1995 presented in these tables was sourced from publications in the Ministry of Health Mortality data and stats series.
Data from 1996–2021 was extracted from the New Zealand Mortality Collection electronic records.