Age and date of birth harmonised standard

Policy details

What is harmonisation?

Harmonisation is the process of making statistics and data more comparable, consistent and coherent.  This harmonised standard sets out how to collect and report statistics to ensure comparability across different data collections in the Government Statistical Service (GSS).

Harmonisation produces more useful statistics that give users a greater level of understanding.

What do we mean by age and date of birth?

Age can be measured in multiple ways. For example, it could be derived from date of birth, asked for age brackets, or asked outright. It can also be output in different ways. For example, age in years, age in brackets, age at time of survey, or age at time of publication. Because of this, it is important to have a harmonised standard for age.

Questions and response options (inputs)

The harmonised questions on this topic are designed to collect basic information, for use in the majority of surveys. They are not designed to replace questions used in specialist surveys where more detailed analysis is required.

The question

Question stem	Response options
What is your date of birth?	Day: [free text]
	Month: [free text]
	Year: [free text]

Only if the respondent refuses to answer date of birth ask for their age.

Question stem	Response options
What is your age?	[Free text]

Using this standard

Guidance for data collection

If this question is used in self-complete surveys, provide separate free text boxes to record day, then month, then year. These should be labelled “day” “month” and “year” above each box. If online, instant validation can be used on the text box to ensure the date entered is possible. Do not include “DD MM YYYY” inside the free text boxes. This is called ghost text and cannot be read by screen readers which makes it inaccessible.

Question placement

Demographic questions such as age or date of birth are usually placed near the start of a survey.

Types of data collection this standard is suitable for

These questions are used in both self-complete (such as online or paper) and interviewer led (such as telephone or face-to-face) surveys.

Using this question in the Welsh language

This harmonised standard was designed in the English language. At present we do not provide a Welsh language translation, as user demand for this standard is UK wide and Welsh language testing has not been completed to ensure a translation is comparable and appropriate. Harmonised standards based on Census research have been tested in the Welsh language, which is why we are able to provide Welsh versions of them. If you are interested in using a Welsh language version of a harmonised standard that has not been translated, please contact us at harmonisation@statistics.gov.uk.

Presenting and reporting the data (outputs)

If date of birth is provided, it is recommended that date of birth input data is translated into age at time of survey before outputting.

The preferred output for age is single year of age. If data quality does not allow this, then there are harmonised groupings which may be used.

Harmonised groupings A, B, C and D are directly comparable and may be collapsed into each other. These can be used as standalone age groups or grouping E may be appended to groupings C, D or F. If appended to grouping F, the first age band of grouping E does not need to be included.

Groupings A, B, C and D can be used for most outputs. Grouping F, however, should only be used for demographic outputs when there are not enough individuals to analyse on single year of age.

Grouping A	Grouping B	Grouping C	Grouping D	Grouping E	Grouping F
0 to 24	0 to 24	0 to 15	0 to 4	85 to 89	0 to 4
25 to 64	25 to 44	16 to 24	5 to 10	90 to 94	5 to 9
65 to 74	45 to 64	25 to 34	11 to 15	95 to 99	10 to 14
75 plus	65 to 74	35 to 44	16 to 19	100 plus, or 100 to 104	15 to 19
	75 plus	45 to 54	20 to 24	105 plus	20 to 24
		55 to 64	25 to 29		25 to 29
		65 to 74	30 to 34		30 to 34
		75 to 84	35 to 39		35 to 39
		85 plus	40 to 44		40 to 44
			45 to 49		45 to 49
			50 to 54		50 to 54
			55 to 59		55 to 59
			60 to 64		60 to 64
			65 to 69		65 to 69
			70 to 74		70 to 74
			75 to 79		75 to 79
			80 to 84		80 to 84
			85 plus		85 to 89
					90 plus

In addition to these groupings, there is also grouping G. This is harmonised and comparable with groupings C and D. Previously, this was recommended to be used for employment and pensions related analysis. While reviewing the recommended output guidance, we have identified that grouping G may no longer be useful for some employment and pension related analysis as the UK state pension age is no longer always 65.  

Grouping G
0 to 15
16 to 64
65+

While we are not removing grouping G, we recommend avoiding its use, as new legislation now puts pensionable age at around 66 to 67. However, in some cases (based on resources and capacity) it may be used as a last resort for employment and pensions related analysis. If grouping G is used, however, methodology reports should acknowledge that age 65 is no longer a reliable cut off for pensionable age. 

Where possible, data should instead be output in relation to whether or not an individual has reached State Pension age (SPa), rather than whether they are over 65. This can be calculated using the respondents date of birth (as collected using this standard), date of data collection, and the State Pension age timetable. Use the table to find the interval the date of birth falls into which will provide the corresponding date SPa is reached. 

To output using SPa, we recommend coding and flagging respondents who have reached SPa. This approach is used in data collection across government. By using the date of birth intervals and the corresponding date SPa is reached, code should repeat in line with the gradual incremental rise and flag those that qualify as reaching SPa. The respondents that are flagged can then be used in employment and pension related analysis. For further advice or information on outputting SPa using coding, please get in touch with Harmonisation@statistics.gov.uk. 

Information on outputting SPa should be included in the methodology report so that users know what the basis for this is. However, this can be as simple as: ‘During this [time period], the pension age rose from x years and y months to x years and y months for women, and x years and y months to x years and y months for men’. If needed, a higher level of detail on methodology can be given.  

Comparability

Outputs that use this standard are comparable with other surveys that also use this standard. However, we would not recommend comparing age outputs using this standard with other outputs that use an alternative measure.

The harmonised question on date of birth is planned to be used on the 2021 Census for England and Wales, the 2021 Census for Northern Ireland and the 2022 Census for Scotland.

NHS are proposing to adopt the harmonised age category D appended with E for some of their analysis, therefore health datasets may be comparable.

Grouping G is intended for pensions and employment related analysis, however due to changes in pension ages, not all pensions related outputs use this. Before comparing pensions related outputs it is important to investigate what they include under each output category.

Further information

In the most recent publication, the main changes to improve the standard suitability for multi-mode use are:

• including guidance on using this standard in self-complete modes, and the introduction of free text boxes labelled as “day”, “month” and “year”
• to reduce cognitive burden, the standard now asks respondents for their age as opposed to their “age last birthday”
• removing the guidance for interviewers to record an estimate if respondent refuses to answer, as it can lead to poor quality data

Related links

Links to demographic information harmonised standards:

• Cohabitation
• Household reference person
• Marital or partnership status
• Full name
• Definition of a household
• Household relationships

Contact

We are always interested in hearing from users so we can develop our work. If you use or produce statistics based on this topic, get in touch by emailing Harmonisation@statistics.gov.uk.

Updates