Quality Statement

Label
Number of motor vehicles - 2023 Census: Information by concept en-NZ
Definition

Number of motor vehicles identifies vehicles that are available for private use by the usual residents of private dwellings. These vehicles must be mechanically operational but not necessarily licensed or with a current warrant of fitness.

Motor vehicles include:

  • business vehicles available for private use by people in the dwelling
  • cars, four-wheel drive vehicles, station wagons, trucks, vans, and other vehicles used on public roads
  • hired or long-term leased vehicles
  • vehicles temporarily under repair.

They do not include:

  • farm vehicles not licensed for road use
  • motorbikes or scooters
  • vehicles used only for business
  • vehicles that belong to visitors
  • vehicles occasionally borrowed from another household.
en-NZ
Overall quality rating

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

en-NZ
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 motor vehicles 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 3 concepts are those that are:

  • 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 motor vehicles 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

Households in occupied private dwellings
‘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 motor vehicles data is classified into the following categories:

Census Number of Motor Vehicles Classification V2.0.0 – level 1 of 2

Code Category
0 No motor vehicle
1 One motor vehicle
2 Two motor vehicles
3 Three motor vehicles
4 Four motor vehicles
5 Five or more motor vehicles
9 Not elsewhere included

Number of motor vehicles uses a 2-level hierarchical classification with level 1 presented in the table above. Follow the link above the table to examine the classification in more detail.

The level 1 residual category ‘Not elsewhere included’ contains the residual categories ‘Response unidentifiable’ and ‘Not stated’.

Number of motor vehicles is output through the recode listed below:

The 2023 Census output classifications for number of motor vehicles is consistent with those used for the 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.

en-NZ
Question format

Number of motor vehicles data is collected from the dwelling form (question 14 paper form).

There was a change made to the question in 2023 to make it clearer that scooters should not be included. In the 2018 Census the question was ‘How many motor vehicles (not counting motorbikes) do people who live here have available to use?’. In the 2023 Census the question was changed to ‘How many motor vehicles (not counting motorbikes or scooters) do people who live here have available for use?’.

The number of motor vehicles question is a combination of tick boxes for no motor vehicles, one motor vehicle and two motor vehicles, and a 2-digit numeric text entry field for three or more motor vehicles.

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

On the online form:

  • only one response could be selected. If ‘none’ was selected, any numerical responses given previously would disappear. Furthermore, a response could not be given in a ‘free text box’ with the respondent having already ticked a tick box option
  • the numeric response box accepted values of up to 99.

On the paper form:

  • responses outside the valid range and multiple responses were possible. These were resolved using edits.

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

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

en-NZ
Examples of how this data is used

Data-use outside Stats NZ:

  • by local government and transport planners to plan transport services
  • to assist in planning the location of public transport services, commercial facilities and welfare facilities
  • to understand access to social and other services
  • to study energy conservation.
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Data sources

The table below shows the distribution of data sources for number of motor vehicles data. All data was from census forms as no alternative data sources were available.

Data sources for number of motor vehicles data, as a percentage of households in occupied private dwellings, 2023 Census
Source of number of motor vehicles data Percent
2023 Census response 91.4
Historical census 0.0
Admin data 0.0
Deterministic derivation 0.0
Statistical imputation 0.0
No information 8.6
Total 100.0
Note: Due to rounding, individual figures may not always sum to the stated total(s) or score contributions.

Editing, data sources, and imputation in the 2023 Census has more information around how data sources are improved by editing.

en-NZ
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).

Percentage of ‘Not stated’ for households in occupied private dwellings:

  • 2023: 8.6 percent
  • 2018: 7.8 percent
  • 2013: 5.0 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 households in occupied private dwellings:

  • 2023: 8.7 percent
  • 2018: 8.3 percent
  • 2013: 5.0 percent
en-NZ
Data quality processes

Overall quality rating: Moderate
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: Moderate 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.

Despite high levels of responses to the question from received census forms, the lack of alternative data sources has resulted in a score of 0.91 leading to the quality score of moderate.

Data sources and coverage rating calculation for number of motor vehicles data, households in occupied private dwellings, 2023 Census
Source for number of motor vehicles data Rating Percent Score contribution
2023 Census response 1.00 91.44 0.91
No information 0.00 8.56 0.00
Total 100.00 0.91
Note: Due to rounding, individual figures may not always sum to the stated total(s) or score contributions.

Consistency and coherence: High quality
Number of motor vehicles 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 lack of alternative data sources means that non-response affects certain subgroups more than others.

Accuracy of responses: High quality
Number of motor vehicles data has only minor data quality issues. The quality of coding and responses within classification categories is high. Any issues with the variable appear in a low number of cases (typically in the low hundreds).

en-NZ
Recommendations for use and further information

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

When using the data, users should be aware that:

  • time series trends across regional councils are mostly consistent with those observed at a national level. Caution should be taken when looking at exact counts of motor vehicles in some smaller areas, as response rates may be lower in some areas compared with the national average. It should be noted that areas impacted by Cyclone Gabrielle tend to have higher levels of ‘No information’. However, these areas also had higher levels of no information in the 2018 Census
  • the proportion of ‘No information’ varies across dwelling types as response rates vary
  • there was a minor change to the classification in 2018, when two additional categories were added to the classification (four motor vehicles and five or more motor vehicles). For time series analysis, 2023 and 2018 Census data can be concorded to the previous classification.

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

Key considerations when comparing motor vehicle information from the 2023 Census with other sources include:

  • census is a key source of information on number of motor vehicles 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 and dwellings in the population, while other sources such as the New Zealand Household Travel Survey are only based upon a small sample of the population
  • the New Zealand Motor Vehicle Register records information about vehicles used on New Zealand roads and the person responsible for their use. It is an admin data source and it does not record availability and use in the same way as the census. The census does not require the cars to be registered to be counted so there may be differences when these two sources are compared.
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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.

en-NZ

Information

History

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Revision Date Responsibility Rationale
31 26/09/2024 10:00:57 AM