A record number of people in the U.S. now live by themselves -- and they spend $1.9 trillion a year. Businesses are beginning to take notice.

By Eric Klinenberg, contributor

FORTUNE -- In 1957, University of Michigan psychology professors Joseph Veroff, Elizabeth Douvan, and Richard Kulka released a survey that examined American attitudes to being single. The findings were stark: 80% of those surveyed believed that people who preferred being unmarried were "sick," "immoral," or "neurotic." At a time when more than 70% of adults were married, it's not surprising that people would express a preference for wedded life. But the scorn certainly sounds jarring to contemporary ears.

Oh, how things have changed. Americans are now within mere percentage points of being a majority single nation: Only 51% of adults today are married, according to census data. And 28% of all households now consist of just one person -- the highest level in U.S. history. That second statistic may appear less dramatic than the first, but it's actually changing much faster: The percentage of Americans living by themselves has doubled since 1960.

The extraordinary rise of living alone is among the greatest social changes since the baby boom. Until recently, no culture in human history had sustained large numbers of people in places of their own. Today more than 40% of households have just one occupant in cities such as Atlanta, Washington, D.C., Denver, St. Louis, and Seattle. In Manhattan, nearly 50% of households consist of a single occupant, a number that seems impossibly high until you discover that the rate is similar in London and Paris, and even higher -- a staggering 60% -- in Stockholm.

http://finance.fortune.cnn.com/2012/01/25/eric-klinenberg-going-solo/