At 81, Stan Piotrowski has no desire for full-time company. He lives alone in Tudor City, an enclave with a very high proportion of single dwellers.

“At this point in my life, I wouldn’t want to live with anybody,” he said. “I want to do what I want to do. If I want to sleep late, I can sleep late.”

Piotrowski may be happily alone in his apartment, but he has plenty of company nationwide. The proportion of Americans who live alone has grown steadily since the 1920s, increasing from roughly 5 percent then to 27 percent in 2013, according to the latest Current Population Survey from the Census Bureau.

The phenomenon, which is most prevalent in cities, raises health and safety issues for local governments.

The growth in the number of men living alone is especially dramatic, rising from less than 6 percent in 1970 to more than 12 percent in 2012, according to a Census Bureau report released last year. Fifteen percent of households are women living alone.

Most single-person households are in large urban areas. In Manhattan and Washington, for example, about half of households have single occupants, and in some neighborhoods the proportion is two-thirds, according to a Stateline analysis of census data.

The areas with the lowest percentage of single-occupant households are in Utah and Idaho. Statewide, Utah’s percentage of single-person households is 19 percent, the lowest of any state, and it has the highest proportion of married-couple families, according to the Census Bureau. Among counties, Madison County, Idaho, originally settled by Mormons, has the lowest number of single dwellers in the nation at 10 percent.

While some attribute the steady increase to breakdown in the American family, a new study of census data suggests that economic factors play a larger role. It points out that the rate of living alone tends to grow fastest during periods of economic expansion.

Other causes for the phenomenon are improving health and finances among older people, and younger people waiting longer to get married, according to the study, which relied on nonpublic details of the census data by Census Bureau demographer Rose Kreider.

Studies have repeatedly found that “Americans prefer privacy in living arrangements, and that increasing economic resources are often used to purchase this privacy in the form of living alone,” the study said.

The dangerous side of elderly people living alone was illustrated in Chicago in 1995, when about 750 people died during a heat wave, many of them elderly poor residents who could not afford air conditioning and did not open their windows or sleep outside for fear of crime. The deaths prompted many localities to fight senior isolation with age-friendly programs and networks.

The District of Columbia reaches out to single senior citizens with its Age-Friendly DC Initiative, which includes block-by-block walks over the summer to check in on seniors living alone and to inform them about transportation, meals and nutrition programs.

AARP is also involved in spreading the word about age-friendly policies, many aimed at preventing isolation by promoting intergenerational social and networking activities.

Another emerging program addressing the issue is the Village to Village Network, which establishes communities, or “villages,” that offer older people help finding services and companionship among their peers as they remain in their homes. Started in Massachusetts, the network includes 120 “villages” across the country and is expanding to Canada, Australia and the Netherlands.

Contact and monitoring can make the difference. When another heat wave struck Chicago in 1999, the city reduced deaths by offering free transportation to cooling centers, making phone calls to check on elderly residents and sending city workers on door-to-door patrols to check on single people.

Middle-age people account for the largest growth in people living alone in recent years, nearly doubling since 1999, according to the Stateline analysis of Current Population Survey data. The 55-to-64 age group has increased from 13 percent to 21 percent of those living alone as of 2013, surpassing those 75 and older, who were the largest component of those living alone in 1999.

There has also been an increase recently in people in their 20s living alone, though it’s down slightly from its peak before the recession in 2008. 2013 marked new highs in living alone for people in their early 30s, while the 35-to-44 age group has dropped by 15 percent.