Correlations in achievement between siblings in general reflect the impact of family and community on individual outcomes. More importantly, since the siblings achievements are contemporaneous, these correlations can tell us much more about social and family effects than intergenerational correlations, since the latter effects are clearly a function of constantly changing circumstances.
An interesting paper from Swedish researchers (What More Than Parental Income, Education and Occupation? An Exploration of What Swedish Siblings Get from Their Parents, by Anders Björklund, Lena Lindahl, and Matthew J. Lindquist – available here) looked at the determinants of siblings performance in terms of future earned income.
Estimates of such siblings-linked correlations in income, per Björklund et al show that more than half of the family and community influences shared by siblings are independent of parental income. This is a powerful result as it suggests that:
- within-family and within-social group factors determining the outcomes for siblings are more important than much-talked about income poverty; and
- positive effects of the family on raising children can potentially partially (but with strong effect) offset adverse effects of income poverty.
“Measures of family structure and social problems account for very little of sibling similarities beyond that already accounted for by income, education and occupation.” In other words, it appears that the measured aimed at directly influencing the actual form of the family structure (a traditionalist family focus etc) and the core social welfare policy instruments (policies aimed at alleviating social disadvantages) hold little promise in enhancing future performance of children beyond the already recognized income and education components.
Unless, that is, these policies are incentivising more parental inputs into raising children: “…when we add indicators of parental involvement in schoolwork, parenting practices and maternal attitudes, the explanatory power of our variables increases from about one-quarter (using only traditional measures of parents’ socio-economic status) to nearly two-thirds.”