Number of motor vehicles 2013 Census (information about this variable and its quality)

##Where the data comes from

Question 18 on the dwelling form.

##How this data is classified

0 No motor vehicle

1 One motor vehicle

2 Two motor vehicles

3 Three or more motor vehicles

7 Response unidentifiable

9 Not stated

For further information about this classification, refer to the:

• 2013 Census data dictionary
• Statistical standard for number of motor vehicles.

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 households in private occupied dwellings.

There must be at least one person usually living in a private dwelling for it to be defined as containing a household. If all the people in a private dwelling were visitors at that dwelling, it does not contain a household and they are excluded from this data.

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

##Non-response and data that could not be classified

Non-response

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

• Non-response rate for 2013: 5.0 percent, of which 4.0 percent were substitute records.
• Non-response rate for 2006: 4.1 percent, of which 2.8 percent were substitute records.
• Non-response rate for 2001: 4.2 percent, of which 2.6 percent 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'.

• 5.0 percent of the subject population was coded to 'Not elsewhere included' in 2013, compared with 4.1 percent in 2006. This category was not present in 2001.

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:

• by local government and transport planners to plan transport services
• to assist in the location of public transport services, commercial, and welfare facilities
• to study energy conservation
• in developing the New Zealand Deprivation Index.

##Data quality processes

Quality level

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.

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

Number of motor vehicles 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 forms 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:

• The online form allowed only one response to be selected for the number of motor vehicles question. If a further response was selected, the response given previously disappeared. Multiple responses to this question were possible when forms were completed on paper.

##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: 5.0 percent, of which 4.0 percent were substitute records.

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

##Comparing this data with previous census data

This data is highly comparable with data from the 2006 and 2001 Censuses. 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.

There have been minor changes to the instructions about what to count as a motor vehicle. The 2013 question stated that scooters and vehicles that could only be used on a farm should not be counted. However, the 2001 question did not have any instructions about whether to count farm vehicles and the 2006 question had no information about whether to count scooters or farm vehicles.

There have also been changes to the guide notes for this question. Some information about what to count was included in the 2001 guide notes and detailed information was provided in the 2013 guide notes, but there were no guide notes for this question in 2006.

These changes to the information in the question and guide notes may have affected the way in which some respondents answered the question. The effects of these changes on the data cannot be quantified but are thought to be minor.

The 'Response unidentifiable' category was introduced in 2006, but this classification change has not affected data comparability because the number of responses in this category is very low.

##Comparing this data with data from other sources

No alternative data source is available from Statistics NZ.

##Further information about this data

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

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