For the lowest-income group in the study, annual costs ranged from $6,490 to $7,560; in the middle-income group, from $9,030 to $10,140; and families earning the most paid from $13,410 to $14,670. These expenditures were tallied for two-child households with married parents; however, the expenses in single-parent families were very similar, with the notable difference that the majority of single moms and dads were in the lower income group.