Quality Statement

Label
Number of children born - 2023 Census: Information by concept en-NZ
Definition

Number of children born is the number of children ever born to each female (sex at birth) aged 15 years and over, who usually resides in New Zealand. Stepchildren, adopted children, foster children, and wards of the state are not included.

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Overall quality rating

High quality
Data quality processes section below has more detail on the rating.

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Priority level

Priority level 3
A priority level is assigned to all census concepts: priority 1, 2, or 3 (with 1 being highest and 3 being the lowest priority).
Number of children born is a priority 3 concept. Priority 3 concepts are given third priority in terms of quality, time, and resources across all phases of the census. Priority level 3 concepts are those that have:

  • data that census would not be solely run for, and information about population groups that could not be captured without being in a census
  • data that is important to certain groups
  • data that can be used to create sampling frames for other surveys.

The census priority level for number of children born remains the same as 2018.
The 2023 Census: Final content report has more information on priority ratings for census concepts.

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Subject population

Female (sex at birth) census usually resident population count aged 15 years and over
‘Subject population’ means the people, families, households, or dwellings that the variable applies to.

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How this data is classified

Number of children born is classified into the following categories:

Number of children born V1.0.0 – level 1 of 2

Code Category Code Category
000 No children 007 Seven children
001 One child 008 Eight children
002 Two children 009 Nine children
003 Three children 010 Ten or more children
004 Four children 555 Object to answering
005 Five children 999 Not elsewhere included
006 Six children

Number of children born uses a 2-level hierarchical classification with level 1 categories presented in the table above.

The level 1 residual category ‘Not elsewhere included’ contains the residual categories ‘Response unidentifiable’, ‘Response outside scope’, and ‘Not stated’. Note, ‘Object to answering’ is a valid response for number of children born data.

Follow the link above the table to examine the classification in more detail.

The 2023 Census classification for number of children born is consistent with that used in 2018 Census.

Standards and classifications has more information on what classifications are, how they are reviewed, where they are stored, and how to provide feedback on them.

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Question format

Number of children born is collected on the individual form (question 28 paper form).

With changes to the sex and gender concepts in the 2023 Census the routing of the online form (described below) and instructional text on the paper form has changed from 2018. The paper form instruction has been updated to be clear that references to male and female are for the concept sex at birth.

There were differences in the way a person could respond between the modes of collection (online and paper forms).

On the online form:

  • built-in routing functionality directed females (sex at birth) aged 15 years and over to the question, while males (sex at birth) and females aged less than 15 years were routed past the question
  • number of children born could only be answered with a single response
  • if a person did not answer the sex at birth question, they were asked the number of children born question. People outside the subject population are not included in output, for example, if sex at birth of male was alternatively sourced
  • only responses within the valid range were possible (between 0 and 20).

On the paper form:

  • it was possible for those outside the subject population to respond to the question (such as males, those under 15 years, and non-residents). People outside the subject population are not included in output
  • multiple responses were possible (for example, ticking both none and entering number of children born)
  • it was possible to provide responses outside the valid range.

Data from the online forms may therefore be of higher overall quality than data from paper forms. However, processing checks and edits were in place to improve the quality of paper form data.

Stats NZ Store House has samples for both the individual and dwelling paper forms.

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Examples of how this data is used

Data-use outside Stats NZ:

  • provides insights into family sizes, childlessness, and fertility rates among different populations, ethnic groups, and birth cohorts.

Data-use by Stats NZ:

  • informs fertility assumptions for population projections.
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Data sources

Alternative data sources were used for missing and residual census responses and responses that could not be classified or did not provide the type of information asked for. The table below shows the distribution of data sources for number of children born data.

Data sources for number of children born data, as a percentage of female (sex at birth) census usually resident population count aged 15 years and over, 2023 Census
Source of number of children born data Percent
2023 Census response 85.9
Historical census 8.6
 2018 Census 6.4
 2013 Census 2.2
Admin data 3.9
Deterministic derivation 0.0
Statistical imputation 0.0
No information 1.6
Total 100.0
Note: Due to rounding, individual figures may not always sum to the stated total(s) or score contributions.

There has been a change in alternative data sourcing methodology for the 2023 Census.

For the 2023 Census, information from historical census and Department of Internal Affairs (DIA) birth data were combined in the following priority order for women of all ages:
  • 2018 Census (plus any DIA births post 2018 Census)
  • 2013 Census (plus any DIA births post 2013 Census)

When no historical census data was available, the number of children born identified from the DIA’s birth records was used directly (including those with no children). This method was used only for women born from 1970 onwards and who gave birth in New Zealand, aligning with the higher quality linking of parent records in the Integrated Data Infrastructure.

For the 2018 Census, historical census data (from the 2013 Census) was used for females aged over 50 years, while DIA birth data was used for women aged 15 to 50 years who gave birth in New Zealand.

Editing, data sources, and imputation in the 2023 Census describes how data quality is improved by editing and how missing and residual responses are filled with alternative data sources (admin data and historical census responses) or statistical imputation. This webpage also contains a spreadsheet that provides additional detail on the admin data sources.

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Missing and residual responses

Missing and residual responses represent data gaps where respondents either did not provide answers (missing responses) or provided answers that were not valid (residual responses).

Where possible, alternative data sources have been used to fill missing and residual responses in the 2023 and 2018 Censuses.

Percentage of ‘Not stated’ for the female sex at birth census usually resident population count aged 15 years and over:

  • 2023: 1.6 percent
  • 2018: 7.5 percent
  • 2013: 7.5 percent

For output purposes, the residual category responses are grouped with ‘Not stated’ and are classified as ‘Not elsewhere included’

Percentage of ‘Not elsewhere included’ for the female sex at birth census usually resident population count aged 15 years and over count:

  • 2023: 1.6 percent
  • 2018: 7.5 percent
  • 2013: 7.6 percent
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Data quality processes

Overall quality rating: High
Data has been evaluated to assess whether it meets quality standards and is suitable for use.

Three quality metrics contribute to the overall quality rating:

  • data sources and coverage
  • consistency and coherence
  • accuracy of responses.

The lowest rated metric determines the overall quality rating.

Data quality assurance in the 2023 Census provides more information on the quality rating scale.

Data sources and coverage: High quality
The quality of all the data sources that contribute to the output for the variable were assessed. To calculate the data sources and coverage quality score for a variable, each data source is rated and multiplied by the proportion it contributes to the total output.

The rating for a valid census response is defined as 1.00. Ratings for other sources are the best estimates available of their quality relative to a census response. Each source that contributes to the output for that variable is then multiplied by the proportion it contributes to the total output. The total score then determines the metric rating according to the following range:

  • 0.98–1.00 = very high
  • 0.95–<0.98 = high
  • 0.90–<0.95 = moderate
  • 0.75–<0.90 = poor
  • <0.75 = very poor.

The high proportion of number of children born data received from 2023 Census forms, alongside the proportion of data sourced from alternative data sources, resulted in a score of 0.96 leading to the quality rating of high.

Data sources and coverage rating calculation for number of children born data, female (sex at birth) census usually resident population count aged 15 years and over, 2023 Census
Source of number of children born Rating Percent Score contribution
2023 Census response 1.00 85.88 0.86
2018 Census 0.90 6.39 0.06
2013 Census 0.84 2.22 0.02
Admin data 0.76 3.94 0.03
No information 0.00 1.58 0.00
Total 100.00 0.96
Note: Due to rounding, individual figures may not always sum to stated total(s) or score contributions.

Consistency and coherence: High quality
Number of children born data is consistent with expectations across nearly all consistency checks, with some minor variation from expectations or benchmarks which makes sense due to real-world change, incorporation of other sources of data, or a change in how the variable has been collected.

The main factor contributing to the variation in data from expectations was the change in alternative data sourcing methodology. In 2023, the increased use of alternative sources has reduced the rate of no information. However, users should be cautious when comparing time series for the 'No children’ category, owing to the increased use of admin data in this category.

Accuracy of responses: Very high quality
Number of children born has no data quality issues that have an observable effect on the data. The quality of coding is very high. Any issues with the variable appear in a very low number of cases (typically less than a hundred).

Accuracy of responses collected from both paper and online forms, and bilingual and English paper forms were very high. Few records required editing in the 2023 Census, largely due to improved scanning quality of paper forms and more scanning repairs.

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Recommendations for use and further information

It is recommended that number of children born can be used in a comparable manner to the 2013 and 2018 Censuses.

Users of this data should be aware that:

  • a different methodology for sourcing alternative data was used in the 2023 Census. While the 2018 method was slightly biased towards females with children, the 2023 method is expected to slightly overestimate the number of women with no children.

Comparisons to other data sources
Although surveys and sources other than the census collect number of children born data, users are advised to familiarise themselves with the strengths and limitations of the sources before use.

Key considerations when comparing number of children born information from the 2023 Census with other sources include:

  • Census is a key source of information on number of children born for small areas and small populations. Many other sources do not provide detail at this level.
  • Census aims to be a national count of all individuals in a population while other sources measuring this variable are only based upon a sample of the population.
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Information by variables from previous censuses

To assess how this concept aligns with the variables from the previous census, use the links below:

Contact our Information centre for further information about using this concept.

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Information

History

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Revision Date Responsibility Rationale
28 26/09/2024 10:00:57 AM