New research into the factors that shape the fertility decisions of teenagers has found that within families, teen births tend to be contagious. The study by the University of Bristol has identified the impact of sibling influences on teenage fertility.
Professor Carol Propper from the Universitys Centre for Market and Public Organisation and colleagues from the University of Bergen and the Norwegian School of Economics, have found that having an elder sister who has a teen birth increases the probability of teenage pregnancy in other siblings.
The ESRC-funded study examined the peer effects within families in teen fertility and analysed census data from 42,606 Norwegian women who were born after the Second World War.
The researchers found that teen motherhood of an older sister has a significant impact, known as a peer effect, on the probability that her younger sister will also have a teen birth. This peer effect was shown to double the probability of having a teen birth from around one in five to two in five.
The findings also reveal that the peer effect is more important the closer sisters are in age, and wears off as the age gap between siblings increases. It is also larger for girls in low-income households, where the sharing of resources across young mothers may be more important.
The study also showed that greater education reduced the probability of a teen birth, but that the influence of a sibling who had a teen birth outweighed the impact of higher education.
Professor Propper said: Previous research has shown that family background and raising the education of girls decreases the chances of teenage pregnancy. However, these findings reveal the positive sibling effect still dwarfs the negative effect of education. These findings provide strong evidence that the contagious effect of teen motherhood in siblings is larger than the general effect of being better educated. This suggests that more policies aimed directly at decreasing teenage pregnancy may be needed in order to reduce teen births.