In 1960, 5.8 million American kids lived in single-parent families. Today, that number has more than tripled, to an astonishing 18 million. Another figure is equally startling: nearly 40 percent of our children don’t live in the same home as their biological father. Today, the number of kids whose parents are divorced is nearly equaled by the number of children in homes where there never has been a dad. One out of three babies in America today are born to unmarried women–a 600 percent increase since 1960. “Children need both a mom and a dad.” Why both? In his recently published book, Life Without Father, Rutgers University sociologist David Popenoe details the unique yin and yang generated by a woman-man parenting team. “Mothers tend to be responsive and fathers firm. Mothers stress emotional security and relationships while fathers stress competition and risk-taking. Mothers typically express more concern for the child’s immediate well-being, while fathers concentrate on a child’s long-term autonomy and independence,” Popenoe says.