From 1970 to today.
No change in the American household has been more pronounced over the last 40 years than the rise of people living alone. In 1970, only 17 percent of U.S. households contained such singletons, solo men and (more often) women getting by without kids, spouses, parents or unrelated roommates. Today, more than a quarter of all households (27 percent total) meet this definition.
Not surprisingly, the share of homes with a married couple and kids inside has plummeted over the same time. Historically, the steady shift looks like this, with a particular jolt in the makeup of American households between 1970 and 1980:
That chart comes from the most recent picture of U.S. households released Tuesday by the Census Bureau, drawing on data from the Annual Social and Economic Supplement, the Current Population Survey and the American Community Survey. Back in 1970, 81 percent of all households were family households, with varying combinations of spouses and children and other relatives. Now that figure is about 66 percent. And the share of married couples with children has fallen in half.
So what has happened in all this time? As the Census Bureau points out, that steep drop in married households has as much to do with changing trends in when people get married and have children, not whether they still follow those rites at all. The average age of marriage has risen by about 5 years since 1970, meaning that many people in their early 20s who would have lived in 1970 with a spouse (and soon after that, babies) today have no spouse as of yet to speak of. Young twenty-somethings have essentially added a stage in their life cycle between moving out of their parents' home and moving into a married household.
Over this same time, the massive baby boom generation has also altered the makeup of the average U.S. household as it has aged. In that decade between 1970 and 1980, many baby boomers left home for the first time, leaving behind a large and sudden cohort of married couples living without children.
The effect of these combined trends – shifting demographics and social norms, a drop in families and a rise in singles – has been that the average size of the American household has fallen dramatically since 1970, from 3.1 people per household to 2.6 today.
As we've written before, American households have been getting smaller as our houses, conversely, have actually been getting bigger. But the disconnect between those two trends may be felt the most strongly by people who live alone, whether they're 22-year-old women who aren't yet married, or 70-year-old retired widows. As more Americans are opting to live alone than ever before, that now seems like an entirely unremarkable choice. But for years we've been building houses for that big nuclear family that's now less common. And housing data released earlier this summer by the Census Bureau, illustrated at right, suggests that the U.S. is now a country where many people live alone in a land of 3-bedroom houses.