|Year of birth of woman||Average completed family size||Number of live-born children (percentages)1|
Table source: Office for National Statistics
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 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
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