Investigating how vocabulary relates to different dimensions of family socio-economic circumstance across developmental and historical time

Social inequalities in child vocabulary persist, despite decades of efforts to understand and reduce them. Different dimensions of socioeconomic circumstances (SEC), such as parent education, income, occupational status, wealth and relative neighbourhood deprivation, are likely to represent different mechanisms of effects on child vocabulary. We investigate which aspects of SEC relate to vocabulary, and whether this is stable over developmental and historical time. Data from two large, national datasets were analysed: the 1970 British Cohort Study (born 1970; N= 14,851) and the Millennium Cohort Study (born 2000-01; N=17,070). Substantial individual differences in vocabulary (ages 3–14) were explained by multiple indicators each making a unique contribution, most notably parent education (partial R2:6.4%-8.5%), income (partial R2: 4.3%-6.4%), and occupation (partial R2: 5.3-8.1). Inequalities were generally stable over developmental and historical time. However, findings suggest a need to focus on widening inequalities both towards the start and end of compulsory schooling.