The rising influence of "all the single ladies"

More and more women are getting married later in life, if at all, and it is changing "everything about the way the nation works."

That's according to New York Magazine writer Rebecca Traister, who explores the rising influence and independence of unmarried women in her new book, "All the Single Ladies."

Between 1890 and 1990, the median age of first marriages for women fluctuated between 20 and 22. That number has now soared to 27. In 1960, 60 percent of young women were married, compared to just 20 percent today, according to the Pew Research Center/U.S. Census Bureau.

Traister says women have historically become "automatically dependent on their husbands," once they've entered marriages.

"I mean our government and our social policies and civil institutions are all built with one kind of society of citizenry pattern in mind - that's the married, still hetero married pair in which you have a male earner and a female domestic laborer - and that's not that way the world works anymore," Traister told "CBS This Morning" Monday.

But Traister says the "new pattern for adult female life" is giving women an "unprecedented level of economics, sexual and social independence that calls for a shift in our social policies, from taxes to housing.

"Even the way the schools let out at three in the afternoon and have big summer vacations - the assumption is there's some number of our population who are going to be home to take care of those children, and the assumption has always been that they're women," Traister said.

The powerful impact of single women also plays out in the world of politics. In 2012, unmarried women made up 23 percent of the electorate and voted for President Obama 67 to 31 over his Republican opponent, Mitt Romney.

The left leaning of unmarried women is consistent today, with a majority skewed towards Democratic candidate Bernie Sanders. Women accounted for 61 percent of Democratic primary voters in South Carolina, according to CBS exit polling, of which unmarried women comprised a bigger percentage.

"Unmarried women vote Democratic. They require sort of a whole new set of social policies that Democrats are more likely to be behind," Traister said.

The presence of women extends beyond the voter demographic as well, with more unmarried women and single mothers entering politics.

As with women, men are also pushing off marriages to later on in life, but the impact is not the same due to historical differences, Traister said.

"They have been more easily able to earn their own livings, to be economically independent, to have sexual lives that were not judged so harshly if they were having sexual lives outside of marriages," Traister said. "That's still relatively new for women as far as being able to have that kind of social independence and have it be a norm rather than a sort of scandalous or pitiable aberration."