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Chapter 1: Background

This chapter discusses important data issues which affect the historical comparability of life tables. These include changes in the measurement of ethnicity and the population since 1950–52 (the first period for which Māori and total New Zealand life tables were prepared). The measurement of ethnic mortality was particularly affected by the introduction of new death (and birth) registration forms in 1995. The preparation of life tables for subnational areas is also covered.

Ethnic life tables

Ethnic concept

The ethnic concept used for the 1995–97, 2000–02, and 2005–07 life tables is the ethnic group or groups that people identify with, or feel they belong to. Ethnicity is self-perceived and people can belong to more than one ethnic group. For example, people may identify with the Māori ethnicity even though they may not be descended from a Māori ancestor. Conversely, people may choose to not identify with the Māori ethnicity even though they are descended from a Māori ancestor. Ethnicity does not equate with birthplace.

In the Census of Population and Dwellings, ethnicity is identified by the person completing the census form. In the case of births and deaths, ethnicity is identified by the person completing the registration form. For births this is usually the parents, while for deaths this is most likely to be the funeral director (on the advice of a family member).

Different ethnic concepts were used for Māori and non-Māori life tables before 1995–97. These are discussed further in the following sections.

Changes to census forms

The ethnicity question used in the five-yearly Census of Population and Dwellings has had frequent changes in the wording of the instructions and tick-box categories. For an extensive list of historical census questionnaires, refer to Statistics NZ (2006). Before 1986, respondents were asked to identify their race or 'degree of blood' in terms of ethnic fractions. From 1986, respondents were asked to identify their ethnic affiliation via tick-box and/or write-in options, but without indicating the relative strength of affiliation. Moreover, the wording of recent census ethnic questions has varied:

  • 1986: “What is your ethnic origin? Tick the box or boxes which apply to you.”
  • 1991: “Which ethnic group do you belong to? Tick the box or boxes which apply to you.”
  • 1996: “Tick as many circles as you need to show which ethnic group(s) you belong to.”
  • 2001 and 2006: “Which ethnic group do you belong to? Mark the space or spaces which apply to you.”

Changes to population measures

The 1996 Census was the first to be followed by a post-enumeration survey which provided estimates of census coverage (net census undercount). This was a catalyst for Statistics NZ adopting the resident population concept for population estimates, projections, and demographic indexes. The 'estimated resident population' is the best available measure of the population that usually lives in an area. It is based on the census usually resident population count with adjustments for non-response to the census ethnicity question, net census undercount, and residents temporarily overseas on census night. The estimated resident population is not directly comparable with census counts because of these adjustments.

Figure 1.01

Figure, Selected Maori Population Measures.

Changes to birth and death registration forms

In September 1995, new birth and death registration forms were introduced carrying a revised question on ethnicity. Previously, the ethnic question on the death registration form asked for the degree of Māori or "Pacific Island" blood, if any, of the deceased person's parents. The new ethnic question is the same, in principle, as the questions used in the 1996 Census onwards. This has resulted in a number of changes:

  • the ethnic concept is now self-identified ethnicity (previously Māori and Pacific respondents were classified by their 'degree of blood')
  • ethnic vital statistics are now available for a wider range of ethnic groups (previously information was sought only for Māori and Pacific groups)
  • ethnic data is now directly available for newborn babies and the deceased (in both cases this was previously derived from ethnicity of one or both parents)
  • multiple response to the ethnicity question is now possible (previously the degree of Māori or Pacific blood, but not both, could be identified)
  • non-response to the ethnicity question can now be quantified.

The introduction of the new registration forms has resulted in a significant increase in the number of deaths (figure 1.02) and births (figure 1.03) identified for each ethnicity.

Figure 1.02

Figure, Deaths by Ethnicity.

Figure 1.03

Figure, Live births by ethnicity of child.

Availability and comparability of ethnic life tables

Statistics NZ has produced period life tables for the mutually exclusive Māori and non-Māori populations in addition to period life tables for the total New Zealand population. Following the introduction of new birth and death registration forms in September 1995, Statistics NZ has also evaluated the production of life tables for other ethnic groups such as Asian and Pacific. However, official life tables for other ethnic groups have not been produced because of the relatively small size of these ethnic populations, relatively few death registrations, and uncertainty associated with ethnic identification and measurement. For example, a person's ethnic identity can change over time and between different data collections, depending on the respondent and the context of collection. Hence, Statistics NZ is not yet confident that life tables provide a statistically robust measure of the mortality and survival experience of these ethnic populations for a given period (eg 2005–07) or over time (eg between 2000–02 and 2005–07), other than for Māori and non-Māori. All ethnic mortality measures, including those for Māori and non-Māori, should be interpreted with due caution.

Customised and non-official life tables for the Pacific and 'European or Other (including New Zealander)' ethnic groups are available on request from Statistics NZ. For more information, and quotes, email demography@stats.govt.nz

There is evidence that Māori deaths were significantly under-reported, and hence non-Māori deaths were over-reported, before the new vitals registration forms were introduced in 1995. Following redesign of the forms, death registrations and population data are broadly comparable for ethnic groups. The 1995–97 Māori and non-Māori life tables published in July 1998 were the first to be constructed using data derived from the new registration forms. However, because numerator-denominator ethnic differences are significant before 1995–97, ethnic mortality measures from 1995–97 are not comparable with those from earlier years. For alternative estimates of life expectancy of different ethnic populations before 1995–97, see Ajwani (2003). Note, however, that these estimates may not be directly comparable with mortality measures produced by Statistics NZ because of differences in both the deaths numerator and population denominator. 

Table 1.01

Summary of Ethnic Concepts, Deaths Measures, and Population Measures
In New Zealand complete life tables
1950–52 to 2005–07

Period 

Ethnic concept

Deaths measure

Population measure

2005–07

Māori life tables based on deaths of people with Māori ethnicity and the population of Māori ethnicity. Non-Māori life tables based on deaths and population not included in Māori life tables.
Both Māori and non-Māori life tables make allowance for deaths and population with no ethnic response.

Deaths registered in New Zealand of people resident in New Zealand.

Estimated resident population at 30 June 2006 (based on census usually resident population count at 7 March 2006).

2000–02

Māori life tables based on deaths of people with Māori ethnicity and the population of Māori ethnicity. Non-Māori life tables based on deaths and population not included in Māori life tables.
Both Māori and non-Māori life tables make allowance for deaths and population with no ethnic response.

Deaths registered in New Zealand of people resident in New Zealand.

Estimated resident population at 30 June 2001 (based on census usually resident population count at 6 March 2001).

1995–97
revised

Māori life tables based on deaths of people with Māori ethnicity and the population of Māori ethnicity. Non-Māori life tables based on deaths and population not included in Māori life tables.
Both Māori and non-Māori life tables make allowance for deaths and population with no ethnic response. Adjustment made to Māori/non-Māori deaths, for undercount of Māori deaths using adjustment ratios presented in Ajwani (2003).

Deaths registered in New Zealand of people resident in New Zealand.

Estimated resident population at 30 June 1996 revised (based on census usually resident population count at 5 March 1996).

 1995–97

Māori life tables based on deaths of people with Māori ethnicity and the population of Māori ethnicity. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no ethnic response.

Deaths registered in New Zealand of people resident in New Zealand.

Estimated resident population at 30 June 1996 (based on census usually resident population count at 5 March 1996).

 1990–92

Māori life tables based on deaths of people with any degree of Māori blood and the population of Māori ethnicity. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths with no indication of degree of Māori blood, and population with no ethnic response.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Census usually resident population count at 5 March 1991.

1985–87

Māori life tables based on deaths of people with 'half or more Māori blood' and the population of 'single ethnic response' Māori. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths with no indication of degree of Māori blood and including population with no ethnic response.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population mean year ended 31 December 1985–87 (based on census night population count at 4 March 1986).

1980–82
revised

Māori life tables based on deaths of people with 'half or more Māori blood' and the population of 'half or more Māori blood'. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood. No adjustment made to Māori/non-Māori deaths for undercount of Māori deaths.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population mean year ended 31 December 1980–82 (based on census night population count at 24 March 1981).

1980–82

Māori life tables based on deaths of people with any degree of Māori blood and the population of 'half or more Māori blood'. Deaths with any degree of Māori blood used as proxy adjustment for undercount of Māori 'half or more' deaths. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population mean year ended 31 December 1980–82 (based on census night population count at 24 March 1981).

1975–77

Māori life tables based on deaths of people with 'half or more Māori blood' and the population of 'half or more Māori blood'. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population mean year ended 31 December 1975–77 (based on census night population count at 23 March 1976).

1970–72

Māori life tables based on deaths of people with 'half or more Māori blood' and the population of 'half or more Māori blood'. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population mean year ended 31 December 1970–72 (based on census night population count at 23 March 1971).

1965–67

Māori life tables based on deaths of people with 'half or more Māori blood' and the population of 'half or more Māori blood'. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population mean year ended 31 December 1965–67 (based on census night population count at 22 March 1966).

1960–62

Māori life tables based on deaths of people with 'half or more Māori blood provided that the remaining blood is European or Polynesian', and the population of 'half or more Māori blood provided that the remaining blood is European or Polynesian'. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population mean year ended 31 December 1960–62 (based on census night population count at 18 April 1961).

1955–57

Māori life tables based on deaths of people with 'half or more Māori blood provided that the remaining blood is European or Polynesian', and the population of 'half or more Māori blood provided that the remaining blood is European or Polynesian'. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population at 30 June 1956 (based on census night population count at 17 April 1956).

1950–52

Māori life tables based on deaths of people with 'half or more Māori blood provided that the remaining blood is European or Polynesian', and the population of 'half or more Māori blood provided that the remaining blood is European or Polynesian'. Non-Māori life tables based on deaths and population not included in Māori life tables, including deaths and population with no indication of degree of Māori blood.

Deaths registered in New Zealand of people resident in New Zealand and people visiting from overseas.

Estimated de facto population at 30 June 1951 (based on census night population count at 17 April 1951).

Subnational life tables

For most subnational areas, death and population numbers are too small to construct reliable complete life tables. However, abridged period life tables, which involve death and population data by age groups (0, 1–4, 5–9, ... 80–84, 85+ years), have been constructed for many subnational areas. Nevertheless, even the abridged life tables must be interpreted with caution. Death and population numbers can fluctuate from year to year. In addition, the stated residence of the deceased may not reflect the geographic area(s) where that person spent most of their life.

For many subnational areas, death and population numbers are also too small to construct reliable abridged life tables. Standardised death rates provide an alternative summary measure of the mortality experience of each area. Like life tables, they allow for the different age-sex composition of each area. Standardised death rates have been calculated for all regional council and territorial authority areas of New Zealand for the periods 1995–97, 2000–02, and 2005–07.

A summary of subnational mortality and longevity trends from 1990–92 to 2005–07 is included in this report. The 1990–92 life tables use a different population measure than later periods (see table 1.02). More detailed results, including abridged life tables for various regions and territorial authority areas, are available on request (email: demography@stats.govt.nz, phone toll-free: 0508 525 525).

Table 1.02

Summary of Deaths Measures and Population Measures
In subnational abridged life tables
1990–92 to 2005–07  

Period

Deaths measure

Population measure

2005–07

Deaths registered in New Zealand of people resident in each area.

Estimated resident population of each area at 30 June 2006 (based on census usually resident population count of each area at 7 March 2006).

2000–02

Deaths registered in New Zealand of people resident in each area.

Estimated resident population of each area at 30 June 2001 (based on census usually resident population count of each area at 6 March 2001).

1995–97
revised

Deaths registered in New Zealand of people resident in each area.

Estimated resident population of each area at 30 June 1996 revised (based on census usually resident population count of each area at 5 March 1996).

1995–97

Deaths registered in New Zealand of people resident in each area.

Estimated resident population of each area at 30 June 1996 (based on census usually resident population count of each area at 5 March 1996).

1990–92

Deaths registered in New Zealand of people resident in each area.

Census usually resident population count of each area at 5 March 1991.

 

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