Child stunting is about more than malnutrition. It’s about favoritism.

Stunting occurs when a child’s height, given their age, is at least two standard deviations below the median of the WHO Child Growth Standards. This is most prevalent in developing countries, where issues like hunger, poverty, and inadequate maternal health care continue to affect children’s growth.

In a new paper in the September issue of the American Economic Review, authors Seema Jayachandran and Rohini Pande find that a preference for the oldest son — who is expected to take care of aging parents, inherit property, and perform post-death rituals — might be responsible for much of the child stunting in India.

Families tend to invest the most in their oldest sons, starting with prenatal care and extending to early childhood tetanus shots and iron supplements. Other siblings, particularly girls, end up without the resources they need to reach a healthy height.

In Figure 1, the authors show how average heights in states in India (the red circles) compare to those in Sub-Saharan African countries (the blue circles), where child stunting also exists but there is not the same preference. The preference for the oldest son explains thirty-two percent of the gap between the two groups.

Figure 1 from Jayachandran and Pande (2017)

Even though both groups experience child stunting, having a preference for the oldest son causes more of it. For example, families with this preference might have one taller boy and multiple stunted children, whereas families without this preference might have multiple medium-height children. So, the family with the preference ends up with the lower average height.

As governments and development agencies try to address child stunting, shifting norms around gender and familial roles could be a meaningful part of the solution.