Over 80% of all the survey subjects had sibling(s).
According to changes in the sibling composition, those who were the only child made up 48.8% of all survey subjects in the 1st survey (aged 6 months) but they had new brother(s) or sister(s) over the years, resulting in a decline in the proportion of those who were an only child to 19.1% by the time of the 5th survey (aged 54 months). Consequently, over 80% of all survey subjects had sibling(s) (Figure 1).
Figure 1 Changes in the sibling composition
|Notes:||The figures are based on the total number of responses to the 1st through 5th surveys, excluding the replies
with gunknownh concerning sibling composition (total number of replies: 37,621).