Single motherhood is becoming less and less common, except among women who are the most financially equipped for it. Government data indicate the number of women having what are called nonmarital children, or children born out of wedlock, has dropped 14 percent in the past decade, except among women in their 30s: unmarried women ages 35-39 are 48 percent more likely to have children out of wedlock than they were a decade ago.

While single parenthood remains widespread and the U.S. birthrate has been declining as a whole, the number can be seen as a reason for optimism for people who have bemoaned the sustained erosion of two-parent homes for children.

In 1980, 78 percent of American children were born into two-parent homes. That number declined steadily for decades, reaching a nadir of about 60 percent in 2007, according to the Center for Disease Control. Through those years, scholarship piled up showing that children raised in one-parent households tend not to do as well in school, are more likely to be unemployed later in life and generally have a tougher go of it in life than children raised in two-parent homes.

The rise in the number of children raised by single parents seemed inexorable, yet following 2007, the share of women having children while they were not married began to decline. Pointing to a single reason for the change is difficult. Some of it could be economic: The U.S. birth rate declined as a whole in the same period, largely because of the recession. In times of economic uncertainty, birth rates tend to go down, and the long recovery following the financial crisis had a drastic effect on population projections for the United States. Yet when the economy finally started to rebound a few years ago, birth rates among married followed suit, but birth rates among the unmarried did not.

Gains in education may tell a small part of the story too. Historically, women without college degrees were more likely to have nonmarital children, yet the percentage of women going to college has grown significantly, even outpacing the gains among men over a similar period.

Birthrates among women with no college education declined sharply during the recession. “This could be deliberate planning, or it could reflect relationship problems or economic stress undermining their family plans,” sociologist Philip Cohen told the New York Times.

Amid this fall sits the unusual stat that unmarried women in their late 30s are having children at much higher rates now than they were at the start of the 21st century. Nearly a third of all unmarried women ages 35-39 had children, the National Center for Health Statistics reported, up from just 20 percent in 2002. Those ages 30-34 posted a healthy increase in birth rate as well, to nearly 60 percent in 2012 from around 40 percent in 2002.

“The delay in general fits a longterm pattern,” Cohen said. “Family formation is increasingly delayed until women are more established.”