This paper empirically investigates the causal effect of having siblings on the cognitive, language, motor, and social-emotional skills of infants under the age of 2 in rural families in Guizhou Province in China. The results are based on data from a survey conducted in 2017. To effectively relieve the endogeneity induced by selection bias, we applied the matching-smoothing (MS) method to evaluate the effects of having siblings. The results show that, first, having siblings produces significant negative impacts on an infant's cognitive, language, and social-emotional skills; second, intrahousehold resource allocation is the mechanism behind the Quantity-Quality (Q-Q) trade-off, and it exerts its effects through two key identified channels-the home environment and parental warmth. By spreading the parents' investment among siblings in terms of both the home environment and parental warmth, having siblings hinders infants' early development. Our findings provide new evidence for the relation between the Q-Q trade-off and early childhood development in rural families in western China.
Keywords: Quantity–Quality trade-off; early childhood development; home environment; intrahousehold resource allocation; parental warmth.