Skip to content

Summary of Statistics Available About Only Children

Released: 16 December 2011 Download PDF

Table 1: Average family size and estimated family size distribution for women who are assumed to have completed their childbearing, by year of birth of woman, 1920 to 1965

England and Wales

Year of birth of woman Average completed family size Number of live-born children (percentages)1
Childless 1 2 3 4+ Total2
1920 2.00 21 21 27 16 15 100
1925 2.12 17 22 28 17 16 100
1930 2.35 13 18 30 19 20 100
1935 2.42 12 15 32 21 20 100
1940 2.36 11 13 36 22 18 100
1945 2.19 10 14 43 21 12 100
1950 2.07 14 13 44 20 10 100
1955 2.02 16 13 41 19 11 100
1960 1.98 19 12 38 20 11 100
1965 1.91 20 13 38 19 10 100

Table source: Office for National Statistics

Table notes:

  1. Percentage of women with 0, 1, 2, 3 or, 4+ children who have completed their childbearing.
  2. Figures may not add exactly due to rounding.

Download table

1. Only children

An only child is a person without brothers or sisters and is generally assumed to be a person who never has siblings during their childhood. A first born child who gains a sibling within a few years would not normally be considered to be an only child. However a child who gains a step- or half-sibling many years later may be thought of as an only child.

The Office for National Statistics does not have the information to determine the number of only children living in the UK, because although there are statistics about children living with any siblings in the same household, it is not possible to determine the number of children with any siblings living elsewhere. However, some insight can still be provided into this subject by examining the number of women who reach the end of their childbearing years having had only one child, and the number of families with only one child living in the household.

2. Proportion of women having one child

Table 1 shows that the most recent group of women to have reached age 45 (who are considered to have reached the end of their childbearing years) were those born in 1965, who had on average 1.91 children. Among women born in 1965, 13 per cent had only one child.

The proportion of women having one child fell from over 20 per cent for women born in the 1920s to 15 per cent among those born in 1935 and has remained around 12-13 per cent among women born in the 1950s and 1960s.

These statistics1 are accurate but not very timely because we need to wait until women reach the end of their childbearing years to determine the number of children they have had. An alternative way to look at only children is to use surveys to determine the number of families with only one child in the household.

3. Number of families with one dependent child living in the household

Figure 1: Families by number of dependent children, 2000, 2005 and 2010, UK

Families by number of dependent children in the family, 2000, 2005 and 2010, UK
Source: Labour Force Survey - Office for National Statistics


  1. Statistics in chart are shown as a percentage of all families with dependent children.

Download chart data

Figure 1 shows that the percentage of families2 with dependent children3 in the UK who had only one dependent child in the household increased steadily from 42 per cent in 2000 to 46 per cent in 2010. This represents a rise from 3.07 million to 3.55 million families.

The figures are based on data from the Labour Force Survey (LFS) on the composition of households at one point in time. In some families containing one dependent child, the child may have a sibling living elsewhere or a non-dependent (adult) sibling in the same household. In these cases the child is not an only child as per the definition of having no siblings. In addition some parents who have one child in the family at the time of the survey may go on to have further children, so not all children in one child families will be only children throughout their childhood.

4. Number of dependent children living in a family with one dependent child

Statistics from the LFS show that in 2010, 3.55 million dependent children in the UK were living in families where they were the only dependent child. This proportion has been rising over time, from 23 per cent of all dependent children in 1997 to 27 per cent in 2010.

The General Lifestyle Survey provides a longer time series back to the 1970s, albeit for Great Britain (excluding Northern Ireland) rather than the UK. In 1972 this source shows that 18 per cent of dependent children were living in families with only one dependent child.

These statistics are similar to those in section 3 above but are expressed in terms of dependent children rather than families. So the proportion of families containing only one child is considerably higher than the proportion of children living in a one child family (because a two-child family will be counted once in the first case but will be counted as two children in the second case).

The statistics do not necessarily indicate that the proportion of only children is increasing. Women have been postponing their childbearing to older ages in recent years; this could be temporarily increasing the proportion of families who have had a first child but not yet had their second.

Source: Office for National Statistics

Background notes

  1. Full information about average family size and the number of live-born children born to women can be found in Cohort Fertility, 2010 which also includes information on projected future family sizes for women born between 1970 and 1995.
  2. A family is a married, civil partnered or cohabiting couple with or without children, or a lone parent with at least one child. Children may be dependent or non-dependent. Further information about families and households can be found in Families and households in the UK, 2001 to 2010.
  3. Dependent children are those living with their parent(s) and either (a) aged under 16, or (b) aged 16 to 18 in full-time education, excluding children aged 16 to 18 who have a spouse, partner or child living in the household.
  4. The estimates in section 4 are subject to the same caveats as in section 3. Therefore estimates of children in one child families will be higher than the actual number of only children as defined in section 1.
  5. Details of the policy governing the release of new data are available by visiting or from the Media Relations Office email:

    These National Statistics are produced to high professional standards and released according to the arrangements approved by the UK Statistics Authority.

Content from the Office for National Statistics.
© Crown Copyright applies unless otherwise stated.