Raised income levels subsequent to welfare reform, both for those in and out of work, may therefore be expected to have a positive effect on children. A review of the evidence on welfare reform and child outcomes in the United States (Waldfogel, 2007) concludes that those most vulnerable to doing poorly as a result of policy changes are the very young (under age two) and adolescents. Detrimental effects are most likely to occur where there are no gains in income, when mothers are working in low-wage or long-hour jobs, or jobs which reduce the amount of parents’ time with children (such as jobs with non-standard work hours or long commutes). The evidence has largely supported investment in early years’ services with Cunha and Heckman (2005) arguing that early intervention to break the link between poverty in childhood and outcomes in later life is crucial because of the way skills are developed: “skill begets skill, and learning begets more learning. Early advantages accumulate, just as early disadvantages do”. While later interventions may still be worthwhile, it is much more costly to intervene to affect outcomes for teenagers.