The effect of differences in outcomes by income is not just a consequence of differences in parental education or ability. Coefficients on adverse outcomes reversed, such that higher scores equal more favourable outcomes. Indeed, some authors have gone as far as to suggest that the entire difference in outcomes between children in lone-parent families and those brought up by two parents can be explained by the associated loss of income rather than the absence of their father per se (Walker and Zhu, 2005). However, maternal employment, while raising the income levels of lone-parent households, may have some adverse effects.