Sex is the distinction between males and females based on the biological differences in sexual characteristics.
In responding to a question on sex, most people are able to classify themselves as either male or female. A person who has undergone sex reassignment is classified to that sex. A person who was of indeterminate sex and who has undergone sex assignment is classified to the assigned sex. Someone who is currently undergoing such procedures and living as the sex that they are taking steps towards, is classified as that sex.
Where the data comes from
Question 3 on the individual form.
How this data is classified
No provision is made for residual categories as, in line with international practice, it is Statistics New Zealand policy to impute missing values for sex data.
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.
The subject population for this variable is the census night population, as sex data is collected for all people in New Zealand on census night. However, data on sex is more often output for the census usually resident population.
The subject population is the people, families, households, or dwellings to whom the variable applies.
Non-response and data that could not be classified
This variable does not have a non-response category.
If a respondent did not complete question 3 on the individual form, a response is imputed. If an individual did not complete a form but there was enough evidence that that person existed in the household, a substitute form was produced and sex was imputed.
Sex imputation supplies sex by using information such as the name of the person or their relationship to others in the household.
If these are not available, a value is assigned randomly, with 49 percent being imputed as male.
Imputation of data for this variable can be done where an entire individual form for a person in a household was not answered, and where an entire household did not respond.
- In 2013, sex was imputed for 5.2 percent of the usually resident population, of which 4.8 were substitute records.
- In 2006, sex was imputed for 4.1 percent of the usually resident population, of which 3.2 were substitute records.
- In 2001, sex was imputed for 4.1 percent of the usually resident population, of which 2.1 were substitute records.
For more information on imputation and substitute records, refer to the 2013 Census data user guide and the paper Imputation and balancing methodologies for the 2006 Census.
How this data is used
Data from this variable is used by:
- local authorities and central government agencies for the development and evaluation of policies, programmes, and services
- market researchers and other research organisations for research into and monitoring of socio-economic changes in the population
- private organisations and businesses in compiling population structure data
- the Ministry of Women's Affairs for policy planning and for monitoring the status of women.
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.
A quality level is assigned to all census variables: foremost, defining, or supplementary.
Sex is a foremost variable. Foremost variables are core census variables that have the highest priority in terms of quality, time, and resources across all phases of a census.
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:
- The online form allowed only one response to be selected for the sex 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.
- On the online form, the sex question had to be answered in order for the respondent to submit the form. Non-response to this question was possible when forms were completed on paper.
Quality assessment of data and data quality issues for this variable
Overall quality assessment
Very high: fit for use – with no data qu ality issues or only very minor data quality issues. 2013 Census variable quality rating scale gives more detail.
Issues to note
- In 2013, sex was imputed for 5.2 percent of the usually resident population, of which 4.8 percent were substitute records.
For more information on imputation and substitute records, refer to the 2013 Census data user guide and Imputation and balancing methodologies for the 2006 Census.
Comparing this data with previous census data
This data is fully comparable with data from the 2006 and 2001 Censuses. Changes in the data over this time period can be interpreted as real changes because there have been no changes in the way the data has been collected, defined, and classified.
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.
Census data is used as the baseline for population estimates and projections so the accuracy of the estimates and projections tends to deteriorate with time elapsed after the census date.
Further information about this data
Contact our Information Centre for further information about using this variable.