Who would you bet is more likely to graduate from college? The yet-to-be born children of Chelsea Clinton and Marc Mezvinsky or Tripp Palin, the child already born to Levi Johnston and Bristol Palin, who became pregnant at 17? Therein lies the secret of America's declining educational performance.

The United States, which once led the world, has fallen to twelfth in the percentage of its citizens that graduate from college, according to a column by Bob Herbert in last Friday's New York Times.

The time has come to admit the truth every parent knows -- childrearing today is harder and more expensive than it was in the era in which America rose to prominence. Higher education became less affordable even before the Great Recession forced the states to slash education budgets, and the loss of close knit communities means that parental supervision has become more important in keeping children out of trouble. In our book Red Families v. Blue Families, we explain that "blue families" have responded to this reality by investing more in each child, and encouraging them to wait to have children until they, too, can bring the emotional and financial resources of independent adults to the task. Chelsea and Marc represent the new ideal, and there is every reason to believe that they will have considerable resources to bring to childrearing. Bristol and Levi, in contrast, represent the outcome of a system that preaches abstinence without the foundation of adult supervision, a promising future, or draconian consequences that once made it work. They bring Tripp into a world that simultaneously says having the child and keeping it is an acceptable choice, but you are on your own in dealing with an environment that provides little support for childrearing.

In another era, marriage would have been the answer. Levi would need to get a job, but jobs were plentiful. Today, the lack a high school diploma keeps him out of the electrician's apprentice program in which he tried to enroll, and the alternatives (outside of cashing in the notoriety that comes from his connection to the Palin family) are bleak. In the meantime, he is likely to father (if he hasn't done so already) other children to whom he contributes little support.

In another era, Bristol may have found married life confining, but the stakes for her have become much higher. Teens who marry young face bleaker financial circumstances, and they have always faced high risks of divorce. Over the last twenty years, the overall divorce rate has leveled off, but the chances that young couples like Bristol and Levi will remain married have worsened appreciably and more women, like Bristol, decide that the prospective groom simply doesn't offer enough to make marriage worthwhile.

For Bristol, marriage itself has risks that extend far beyond the discovery that Levi is a cad. If marriage were to make it more likely that she has a second child soon after the first or that she relies on her husband's earnings rather than her own, both her marital happiness and her prospects for life without Levi decline. Two career couples and stay-at-home moms with successful husbands are both doing well; financially stretched couples where the mother has to work because of the father's failure to earn enough to support the family are not -- and working class men now earn less in real dollar terms that they did a generation ago. Many parents, apparently like the Palins, experience relief when their daughters fail to marry the fathers of their children.

All of this magnifies the uncertainties for Tripp's future. The stimulation a child receives during the first three years, and parental ability to provide that interaction, increases with the parents' education and the support the caretaking parent has from others. Single mothers are stretched thin. As the child grows, the child needs medical care, parents who can supervise homework and afterschool activities, love and supervision. College graduates are more likely to be employed in workplaces that offer health insurance, flexible hours, and parental leave, and they are more likely to live in neighborhoods that still have effective public school.

As high school students start to plan for college, those who are most optimistic about their futures are also more likely to remain abstinent (and to use contraception if they don't). And with more students unable to afford the traditional college experience, the odds of keeping less hopeful students on track become more difficult.

While we emphasize that blue states do better than red states in delaying marriage and investing in children, the differences are ones of degree. Sarah Palin is a hero to her constituency because she and Bristol both had inconvenient children rather than resort to abortion. Her supporters realize that the conservative elite more commonly follows the blue prescription -- invest heavily in the children you have and protect them from the youthful temptations that threaten the futures of the next generation. The Tea Partiers just do not believe that their tax dollars should be used to help the children of others; indeed, the Republicans in Congress are blocking efforts to provide emergency funding to prevent teacher lay-offs. The modern economy and the triumph of conservative economics magnify inequality and make the stakes of childbearing that much higher. Hillary -- not Sarah -- is the Mama Grizzly in this story.