Mother or market? Effects of maternal employment on the intellectual ability of 4-year old children

data set to investigate the impact of maternal employment onchildren's intellectual ability, as measured at the age of 4 by using the Peabody Picture Vocabulary Test (PPVT). Results from multivariate regression a alysis show a statistically significant adverse effect of mother's employment onchildren's intellectual ability, but only for boys in higher income families. Furthermore, thenegative impact was related to the timing of maternal employment: employment during the boys ' infancy had a statis-tically significant egative effect on PPVT scores at the age of 4. This pattern was not found for girls, for children in low-income families, or for families in which mothers resumed their employment after the child's first year of life. The impact of other demographic trends in recent yearsdeclining fertility and rising marital instabil-ity-are also investigated. The results show an adverse effect of the presence of other siblings on children's PPVT scores; but holding family income constant, he effect of the parents ' marital status on children's intellectual ability isnot statistically significant. In addition, several family background factors are highly correlated with children's test scores