More Kids, More Conflict? Family Size and Domestic Violence in a High-Fertility Setting

Does the number of children in a household affect the prevalence of domestic violence? This study examines the causal impact of family size on intimate partner violence (IPV) using nationally representative survey data from Samoa, a country with one of the highest fertility rates globally. Employing an instrumental variable (IV) strategy, the analysis leverages same-sex sibling pairs as a plausibly exogenous instrument for family size. The results establish a direct causal link between family size and IPV, with each additional dependent child increasing IPV likelihood by 6 percentage points—a 15 percent rise from the mean—particularly for physical and sexual violence. Mechanism analysis identifies three key channels: (1) economic constraints, (2) bargaining power and control, and (3) norms and attitudes towards IPV. Larger families exacerbate household overcrowding, reduce female labour force participation, limit womenʼs control over household earnings, healthcare, and contraception decisions, reinforce IPV-condoning attitudes, and escalate female-perpetrated violence due to heightened caregiving burdens. These findings align with a partial non-cooperative household model, highlighting the interplay between resource dilution, intra-household bargaining, and IPV risk. The results underscore the importance of expanding womenʼs agency in reproductive and economic decisions while addressing structural constraints and norms that perpetuate violence.