Birth Order Effects Needn't Be Biological

Birth order effects—where siblings systematically differ based on the order they were born in—are a subject of perennial interest and equally frequent consternation. Most people have siblings, so there’s a reason they’re interested; the source of consternation is less obvious and has to do with the fact that birth order effects are often hard to replicate. There are two big reasons for their replication issues: Parents are inequality averse and; Parents learn how to parent as they age. Some examples will suffice. Terskaya had access to large-scale census data from Mexico circa 2010. She used the variation in family size and child disability status to show that parents are averse to inequality. The method behind this is simple: There’s an education deficit associated with being disabled. In families with only one child, parents can’t show inequality aversion, but when there are multiple children, they can. In multi-child families, it turns out the disability-associated education deficit

Birth order effects—where siblings systematically differ based on the order they were born in—are a subject of perennial interest and equally frequent consternation. Most people have siblings, so there’s a reason they’re interested; the source of consternation is less obvious and has to do with the fact that birth order effects are often hard to replicate. There are two big reasons for their replication issues: Parents are inequality averse and; Parents learn how to parent as they age. Some examples will suffice. Terskaya had access to large-scale census data from Mexico circa 2010. She used t