Yet our relationship with solitary life has undergone a radical shift in the recent past. So argues NYU sociology, public policy, and media professor Eric Klinenberg in Going Solo: The Extraordinary Rise and Surprising Appeal of Living Alone — an ambitious exploration of what Klinenberg calls the “remarkable social experiment” that our species has embarked upon over the past half-century, juxtaposing the numbers with the enduring social stigma around singleness.

Until recently, most of us married young and parted only at death. If death came early, we remarried quickly; if late, we moved in with family, or they with us. Now we marry later. We divorce, and stay single for years or decades. We survive our spouses, and do whatever we can to avoid moving in with others — even, perhaps especially, our children. We cycle in and out of different living arrangements: alone, together, together alone […] [T]oday, for the first time in centuries, the majority of all American adults are single. The typical American will spend more of his or her adult life unmarried than married, and for much of this time he or she will live alone.

Klinenberg paints an even more vivid picture by the numbers:

In 1950, 22 percent of American adults were single. Four million lived alone, and they accounted for 9 percent of all households […] Today, more than 50 percent of American adults are single, and 31 million — roughly one out of every seven adults — live alone.

[…]

People who live alone make up 28 percent of all U.S. households, which means that they are now tied with childless couples as the most prominent residential type — more common than the nuclear family, the multigenerational family, the roommate or group home.

To be sure, this trend is far from confined to the U.S. — the four countries with the highest rates of solo living are Sweden, Norway, Finland, and Denmark, where up to 45% of all households contain just one person. “By investing in each other’s social welfare and affirming their bonds of mutual support,” Klinenberg argues, “the Scandinavians have freed themselves to be on their own.”

"The typical American will spend more of his or her adult life unmarried than married, and for much of this time he or she will live alone."

Now if we could just get single people to vote, they'd form a powerful voting block.

How in today's world are we living alone? 

I'm curious how we might reconcile people as living alone if they spend all their time online or out and about with others...Maybe we need clearer unambiguous definitions of solitude, cultural and/or community isolation and loneliness.  

These are not the same things.

What you've described is a world in which people can live singly but not feel lonely.  Indeed, not BE lonely.  Singles no longer have to pay the price of social isolation for a solitary domestic situation.

This reminds me of James Friel's essay on the BBC a while ago, which interested me enough at the time that I still remember many of his words:

James Friel, November 7th 2012:   http://www.bbc.co.uk/podcasts/series/fourthought/all

Transcript:  http://www.bbc.com/news/magazine-20219349

Damn that's good.  Thanks for sharing it.  Back for a re-read.

Powerful:

In the world through which we move, increasingly, we do not expect our relationships to endure. Increasingly, our relative affluence and advances in new technology allow us to live comfortably alone.

Increasingly, this is what we seem to be doing: we are choosing to live alone. We need stories not about how to become couples. They are legion. We need stories about how to be single, and how to be kept amazed and awake by a joy of our own manufacture.

Although I was born single, I never considered that this would continue to be my fate.

"No one is supposed to be single. To be single must mean to be lonely. But far lonelier are those who fear being alone. Namely the “I” who is incomplete without “You”; the “Me” who is without substance or purpose unless rhymed with a “We”; those tyrannised by the need - no, the obligation - to go about this world in pairs."

Pairs tend to think the world should be in pairs. It's how they see the world.