MiSoC’s Birgitta Rabe and Cheti Nicoletti (University of York) looked at sibling spillover effects in cognitive skills, and the direct effects an older sibling has on his or her younger sibling (Nicoletti and Rabe, 2014). The researchers looked at the variation in school test scores across three subjects at age 11 and 16 and the variation in the composition of school mates between siblings. These two sources of variation have previously been separately used to identify school peer effects, but never in combination. By combining them, they were able to identify a sibling spillover effect that is net of unobserved child, family and school characteristics shared by siblings.
The research shows that there are sizeable spillover effects from the older sibling to the younger but not vice versa, and that these are larger for higher than lower attaining pupils. Because children from deprived backgrounds are more likely to have a low attaining older sibling than children from more affluent backgrounds, they tend to benefit less from these positive spillovers. The study finds that sibling spillovers account for a non-negligible proportion of the attainment gap between low and higher income pupils in England. Investments into children from deprived backgrounds have the potential to close such gaps through the positive effects on younger siblings.