The trend away from marriage accounted for almost half the increase in child income inequality and more than the entire rise in child poverty rates, measured from 1971 to 1989:

Robert I. Lerman, "The Impact of the Changing US Family Structure on Child Poverty and Income Inequality," Economica, May 1996, pp. S119-S139. http://ideas.repec.org/a/bla/econom/v63y1996i250ps119-39.html