Disparities in Children’s Vocabulary and Height in Relation to Household Wealth and Parental Schooling: A Longitudinal Study in Four Low- and Middle-Income Countries
Children from low socio-economic status (SES) households often demonstrate worse growth
and developmental outcomes than wealthier children, in part because poor children face a
broader range of risk factors. It is difficult to characterize the trajectories of SES disparities in
low- and middle-income countries because longitudinal data are infrequently available. We
analyze measures of children’s linear growth (height) at ages 1, 5, 8 and 12y and receptive
language (Peabody Picture Vocabulary Test) at ages 5, 8 and 12y in Ethiopia, India, Peru and
Vietnam in relation to household SES, measured by parental schooling or household assets. We
calculate children’s percentile ranks within the distributions of height-for-age z-scores and of
age- and language-standardized receptive vocabulary scores. We find that children in the top
quartile of household SES are taller and have better language performance than children in the
bottom quartile; differences in vocabulary scores between children with high and low SES are
larger than differences in the height measure. For height, disparities in SES are present by age
1y and persist as children age. For vocabulary, SES disparities also emerge early in life, but
patterns are not consistent across age; for example, SES disparities are constant over time in
India, widen between 5 and 12y in Ethiopia, and narrow in this age range in Vietnam and Peru.
Household characteristics (such as mother’s height, age, and ethnicity), and community fixed
effects explain most of the disparities in height and around half of the disparities in vocabulary.
We also find evidence that SES disparities in height and language development may not be fixed
over time, suggesting opportunities for policy and programs to address these gaps early in life