Sex is typically assigned based on a person’s physical and biological features. These sets of biological characteristics are not mutually exclusive, as there are individuals who possess both, but these characteristics tend to differentiate humans as males or females. Sex may be understood as the sex recorded on an individual’s birth certificate or gender recognition certificate.
The terms sex and gender are often used interchangeably. Gender can be used as another term for sex where binary options are required.
It is important to note that sex and gender are two separate concepts, where gender is not collected as a binary variable. However, they are interrelated. Therefore, care should be taken when comparing counts for sex with counts for gender.
Sex refers to the biological and physiological characteristics that define an individual to be either male or female.
This harmonised standard presents guidance on how sex can be defined, measured and presented in a more consistent manner.
Data on sex is important to allow for informed decision making and planning by Government. This information is crucial in measuring certain health and demographic indicators, such as life expectancy. Accurate data on sex are useful for policy formation across a range of fields, such as health, crime and education.
Many data collections require information on the sex of individuals. When collecting data on this topic, the following question is recommended:
What is your sex?
The standard question on this topic is designed to collect information, for use in the majority of surveys or data collections. However, it is not intended to replace questions already in use for specialist surveys where more detailed analysis is required.
The terms sex and gender are often used interchangeably. Gender can be used as another term for sex where binary options are required. Gender may also be used as set out in the CSO Data Standard for Gender where response options are not confined to a binary, male or female, categorisation.
Alternative questions recognise that some surveys and data collections require a level of flexibility in question structure. In such circumstances, the following alternative question can be used:
What was your sex at birth?
The standard response options remain unchanged to ensure harmonisation to the standard.
It is recommended that the use of the alternative question for sex [What was your sex at birth?] is used in conjunction with the standard question for gender [What is your gender?] to allow for the identification of all gendered populations.
The following list of response options represents the basic level of detail that the CSO recommends should be gathered in data collection.
| Standard Response Options and Codes for Sex | |
| 10 | Male |
| 20 | Female |
The standard response options and standard reference classification provided are based on recommended categories derived by the Census Advisory Group for the 2024 Census Pilot.
| Description of Standard Response Options for Sex | |
| Male | An individual whose sex recorded on a birth certificate or gender recognition certificate is male. |
| Female | An individual whose sex recorded on a birth certificate or gender recognition certificate is female. |
| Standard Reference Classification for Sex | |
| 10 | Male |
| 20 | Female |
If more detailed breakdowns are required, please consult classifications@cso.ie
| Concept name | Sex |
| Variable name | SEX_CSO |
| Format type | Character code |
| Guideline Version | 1.0 |
| Guideline Release date | 18 October 2024 |
| Valid to | 18 October 2027 |
| Owner | Central Statistics Office (CSO) Classification Standardisation Team |
| Audience | Policy makers, system developers and producers or users of statistics |
| Contact | classifications@cso.ie |
This data standard will be regularly reviewed and updated to ensure it remains current and aligned with any changes in regulations or best practices. The validation period for this standard is three years.
We are always interested in hearing from users so that we can develop our work.