parent who works at least 20 hours per week (Wertheimer, 1999). Over half of children in poor, married-couple families and 30 percent of poor children in single-mother families have parents who work these substantial hours. Both Hispanic and black families are more likely than white families to be poor, despite the presence of working adults.

The few studies that have focused on maternal employment among low-income children suggest that they are not hurt by and may benefit from maternal employment, particularly with regard to cognitive outcomes (Alessandri, 1992; Hoffman et al., 1999; Moore and Driscoll, 1997; Vandell and Ramanan, 1992). In fact, there appears to be a more consistent advantage of maternal employment for children in working class than in middle class families (Desai et al., 1989; Gold and Andres, 1978; Hoffman, 1979; Zaslow, 1987), perhaps as a result of its positive effects on the mother's sense of well-being, the father's involvement in child-care activities, and the quality of parenting (Hoffman et al., 1999). The limited evidence that is available suggests that infants and toddlers fare better in working-poor families than in poor families in which the parents do not work or work minimally (NICHD Early Child Care Research Network, 1999b). Yet those in working families that are not living in poverty do substantially better than either group of children living in poverty. The children 's better adjustment is seen on measures of cognitive, language, and social development. This pattern of child outcomes is, however, largely attributable to differences across these three groups of families in demographic characteristics (e.g., mothers' education, family size), mothers' depression and social support, and parenting quality and attitudes. New evidence from experimental studies of welfare reform (discussed below) are beginning to expand understanding of how parents' transition to work—often substantial hours of work—affects young children living in poverty.

The corresponding literature on how fathers' loss of work and unemployment affect children has emphasized the influence of these circumstances on harmful family dynamics. Unemployment increases financial strain, which in turn may compromise parent-child relationships by creating tension and hostility as well as reducing warmth and supportiveness in the home. These adverse home environments have been found to have negative consequences for children's development in the short and long term (Conger and Elder Jr., 1994; McLoyd, 1989; Tomblin et al., 1997).

Investigators have also explored to what extent the circumstances and features of work, such as the flexibility of one's work hours, the extent of control over the day-to-day nature of work and the absence of repetitious and boring tasks or the presence of challenging tasks, account for the effects of maternal employment on children (Alessandri, 1992; Greenberger and O'Neil, 1991; Howes et al., 1995a; Jencks et al., 1988; Menaghan and