College costs loom large in the parental mind. According to a 2013 report by Sallie Mae, half of parents are putting away money for their kids' education. Those who aren't are fretting about it, saying that they feel "frustrated," "overwhelmed" and "annoyed" when they think about college savings. But most parents will deal with an even larger kid-related expense long before college, and it's a cost that very few of them are as prepared for. That expense is day care.

A report last fall by Child Care Aware America, a national organization of child-care resource and referral agencies, found that the annual cost of day care for an infant exceeds the average cost of in-state tuition and fees at public colleges in 31 states. The biggest gap is in New York, where day care will set you back nearly 15 grand, but in-state college tuition is only $6,500 -- a difference of over $8,000. Massachusetts, Maryland, Colorado and Oregon also have large gaps, driven primarily by the high cost of day care in those states. At the other end of the spectrum is South Carolina, where in-state tuition is higher than the cost of day care by about $4,000 a year.

The variation between states is due to differences in costs of living, the regulations and licensing requirements in each state, and the amount of money each state spends on higher education. In South Carolina, for instance, in-state tuition is so high partly because the state reduced higher ed funding by 67 percent from 1980 to 2011, according to the American Council on Education.

While parents have years to prepare for college costs, there is literally no time to save for child care -- a baby is born, and parents typically have to go back to work in just a few weeks' time. We accept that it typically takes 18 years to sock away a sizeable-enough college nest egg. Considering that child care is an equivalent, if not greater, expense and that the average maternal age at first child birth is 26, this suggests that we should similarly start putting money away for day-care expenses when we're roughly 8 years old. Sorry, kids: Your allowance money is going to the day-care fund now.

Obviously this isn't a realistic scenario, but it does raise the question: How do we pay for child care? A report out Tuesday by the Pew Research Center finds that an increasing number of parents are simply avoiding child care costs by staying at home. Nearly 30 percent of moms stay at home now, up from only 23 percent in 1999. For many families it simply makes more financial sense for a parent to stay home with a young child than it does to incur thousands of dollars in day-care costs. Pew reports that only five percent of "U.S. married stay-at-home mothers (with working husbands) had at least a master’s degree and family income exceeding $75,000." This suggests that stay-at-home motherhood is primarily increasing among the lower and middle classes, and that it's driven primarily by having too little money, rather than too much of it.

Parents fretting over college costs can at least console themselves with the notion that there is a good deal of financial aid available for students who need or deserve it. But there are no merit-based scholarships for day care.