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Number of children born alive


The number of children born alive is the number of children ever born alive to each female aged 15 years and over, who usually resides in New Zealand. Foetal deaths and stillborn children are not included. Stepchildren, adopted children, foster children, and wards of the State are also not included.

The question on number of children born alive is cyclical. It was first asked in the 1981 Census of all women aged 15 years and over, and repeated in the 1996, 2006, and 2013 Censuses.

Where the data comes from

Question 25 on the individual form.

How this data is classified

00 No children

01 One child

02 Two children

03 Three children

04 Four children

05 Five children

06 Six children

07 Seven children

08 Eight children

09 Nine children

10 Ten or more children

55 Object to answering

77 Response unidentifiable

88 Response outside scope

99 Not stated

For further information about this classification, refer to the:

For background information on classifications and standards, refer to the Classifications and related statistical standards page.

Subject population

The subject population for this variable is the female census usually resident population aged 15 years and over.

The subject population is the people, families, households, or dwellings to whom the variable applies.

Non-response and data that could not be classified

Number of children born alive includes a category 'Object to answering'. For example, some women who have had a stillbirth may find this question difficult (as a stillbirth is not counted). Although women can refuse to answer this question, they may still prefer not to respond at all, which could contribute to the higher non-response rate for this variable.


The non-response rate is the percentage of the subject population that was coded to ‘Not stated’. 'Non-response' is when an individual gives no response at all to a census question that was relevant to them.

  • Non-response rate for 2013: 7.5 percent, of which 4.7 were substitute records.
  • Non-response rate for 2006: 6.7 percent, of which 3.3 were substitute records.
  • Non-response rate for 1996: 5.6 percent, of which 2.8 were substitute records.

Not elsewhere included

Non-response and responses that could not be classified or did not provide the type of information asked for are usually grouped together and called 'Not elsewhere included'.

  • 7.6 percent of the subject population was coded to 'Not elsewhere included' in 2013, compared with 7.0 percent in 2006 and 5.6 percent in 1996.

For more information on non-response and substitute records, refer to the 2013 Census data user guide.

How this data is used

Data from this variable is used: 

  • to help build accurate models of the population structure and changes to it, to inform research and policy
  • in combination with other census variables, to provide valuable insights into the different population profiles between groups and small areas in New Zealand
  • to provide information on changes in the population age structure, the changing dynamics of family and family size, childlessness, comparisons between subgroups, differences in fertility between ethnic groups, age groups, and other key variables; and as an indicator of women's roles over time.

Data quality processes

All census data was checked thoroughly during processing and evaluation, to ensure that it met quality standards and is suitable for use. These quality checks included edits.

All data must meet minimum quality standards to make it suitable for use.

Quality level

quality level is assigned to all census variables: foremost, defining, or supplementary.

Number of children born alive is a supplementary variable. Supplementary variables do not fit in directly with the main purpose of a census, but are still important to certain groups. These variables are given third priority in terms of effort and resources.

Mode of collection impacts – online form compared with paper form

The online form had built-in editing functionality that directed respondents to the appropriate questions and ensured that their responses were valid. As a result of this, data from online forms may be of higher overall quality than data from paper forms. The significance of this will depend on the particular type of analysis being done. There will always be a mode effect but this cannot be measured. Statistics NZ design and test to minimise the effects of mode for all questions.

There were differences between how the forms were completed online and on paper for this variable:

  • On the online form, only people who gave a New Zealand address in question 5 and were 15 years of age or older were able to respond to the number of babies given birth to question. When forms were completed on paper it was possible for overseas visitors and respondents under 15 years of age to respond to this question.
  • The online form did not allow inconsistent multiple responses to the number of children born alive question. If 'None' was selected, the number of children born alive could not be answered and vice versa. (However, 'Object to answer' could be selected with any other option or on its own.) Inconsistent multiple responses to this question were possible when forms were completed on paper.
  • On the online form, non-numeric answers, negative numbers, or responses greater than 99 for the number born alive were not possible. On the paper form it was possible for a respondent to give a non-numeric answer, a negative number, or a number greater than 99, even though the space provided only allowed for a one- or two-digit answer.
  • On the online form, if 'Male' was selected in Question 3, this question was disabled. On paper forms, it was possible for a male respondent to fill in number of babies given birth to.

Quality assessment of data and data quality issues for this variable

Overall quality assessment

High: fit for use – with minor data quality issues only. 2013 Census variable quality rating scale gives more detail.

Issues to note

  • Non-response rate for 2013: 7.5 percent, of which 4.7 were substitute records.
  • Exercise caution when cross-tabulating by single year of age.

For more information on substitute records, refer to the 2013 Census data user guide.

Comparing this data with previous census data

This data is highly comparable with the 2006 Census data. Changes in the data over this time period can generally be interpreted as real changes. There may be a small component of change over time that is due to minor changes in the collection, definition, or classification of the data.

This data is broadly comparable with the 1996 Census data. Changes in the data over this time period may be partly due to changes in the collection, definition, or classification of the data rather than to real change.

This data was not collected in the 2001 Census.

There are issues affecting the comparability of 2013 and 2006 data with 1996 Census data:

  • The level of data quality achieved was higher in 2013 and 2006 than in 1996, due to improvements in processing technology.
  • The 2013 and 2006 data was not subject to the same type of editing as the 1996 data. This affects the comparability of the data for younger females. If the editing approach used in 1996 had been followed in 2013 and 2006, then the number of children born alive to younger females may have been edited to a lower number in a few instances.

Comparing this data with data from other sources

Census is the only information source that provides comprehensive information for small areas and small populations. However alternative sources of information about this subject are available:

Data from these alternative sources may show differences from census data for several reasons. These could be due to differences in scope, coverage, non-response rates, data being collected at different periods of time, alternative sources being sample surveys and as such subject to sampling errors, or differences in question wordings and method of delivery (self-administered versus interviewer-administered). Data users are advised to familiarise themselves with the strengths and limitations of individual data sources before comparing with census data.

Information from the births data has national coverage and is provided quarterly while census data is generally available every five years. Births data only provides information on women giving birth in that year and does not provide information on childlessness, or overseas births to New Zealand women; and cannot be cross-classified by social or economic variables. Census data is able to provide this information.

Further information about this data

All percentages in census publications have been calculated using 'Total stated' as the denominator.

When using this data, be aware of the following:

  • Respondents have the option of objecting to answer this question. In 2013, 2.8 percent of those who answered the question marked 'Object to answer', compared with 3.0 percent in 2006 and 5.3 percent in 1996.
  • Some males answered this question although this was not an option on the online form. It is also important to note that in some cases the respondent may have marked the wrong sex rather than it being a case of a male answering this question.
  • The instruction used on the 1996 Census form to ‘Count only any who were born alive’ was not used in 2006 or 2013.

Contact our Information Centre for further information about using this variable.

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