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More than 11 million U.S. parents – or 18% – were not working outside the home in 2016, according to a new Pew Research Center analysis of U.S. Census Bureau data.

Despite fluctuations, rate of state-at-home parenting is similar to what it was a quarter-century agoThe stay-at-home share of U.S. parents was almost identical to what it was in 1989, but there has been a modest increase among fathers. The share of dads at home rose from 4% to 7%, while the share of moms staying at home remained largely unchanged – 27% in 2016 versus 28% about a quarter-century earlier. As a result, 17% of all stay-at-home parents in 2016 were fathers, up from 10% in 1989, the first year for which reliable data on fathers are available.

The share of stay-at-home parents in the United States has fluctuated in recent decades. Around 2000, the share of stay-at-home moms hit a low of 23%; the overall share of stay-at-home parents dipped to 15%. But in the immediate wake of the Great Recession, rates of stay-at-home parenting rose to 20% in 2010, driven in part by parents who were at home because they were unable to find work. This was particularly true of stay-at-home fathers, one-third of whom reported they were home for this reason in 2010.

Three-fourths of stay-at-home moms, one-fourth of dads are home to care for familyHowever, the long-term uptick in dads at home is not driven solely by economic factors. The modest increase is apparent even after excluding those who were home due to unemployment. Furthermore, a growing share of stay-at-home fathers say they are home specifically to care for their home or family, suggesting that changing gender roles may be at play. About a quarter (24%) of stay-at-home fathers say they are home for this reason. Stay-at-home mothers remain far more likely than dads to say they are home to care for family – 78% say so.

More stay-at-home dads among Millennials than among Gen X

In 2015-16, 21% of Millennial parents (ages 20 to 35 at the time) were stay-at-home parents, while that figure stood at 17% among Gen X parents when they were the same age in 1999-2000.

Three-in-ten Millennial mothers ages 20 to 35 were at home with their children, compared with 25% of Gen X mothers a generation earlier. Among Millennial dads, 6% were home with their children in 2016, compared with 3% of Gen X fathers when they were a comparable age.

While the share of stay-at-home fathers is higher among Millennials, the share who are home specifically to care for their family has ticked up modestly: 23% of Gen X stay-at-home fathers around 2000 said they were home to care for family, compared with 26% of Millennial stay-at-home dads today.

The profile of stay-at-home parents varies depending on the reason they are at home

Stay-at-home parents who are home to care for family are more educated, less likely to be in povertyAmong all stay-at-home moms and dads, those who are home to care for family are more likely to have a college degree than stay-at-home parents who are home for other reasons. A quarter of dads who are home to care for family have a college degree, compared with 17% of dads who are home for other reasons. Among stay-at-home moms, 29% of those who are caring for family have a college degree, compared with 18% of those home for other reasons. In addition, both mothers and fathers who stay at home to care for family are far more likely than those at home for other reasons to have a working spouse.

These patterns likely contribute to the fact that stay-at-home parents who are home primarily to care for their family are less likely to be living in poverty than other stay-at-home parents. This is particularly true of mothers: A quarter of those home to care for family are in poverty, compared with 41% of those home for other reasons. (By comparison, 8% of working dads and 9% of working moms are living in poverty.)

Stay-at-home parents home to care for family are also more likely to have a young child, and are a bit younger than other stay-at-home parents: 68% of fathers home to care for family are younger than 45, compared with 52% of fathers home for some other reason. Among moms, 80% of those home to care for family are younger than 45, compared with 71% of those home for another reason.

This analysis includes all parents ages 18 to 69 who report living with at least one of their own children (biological, step or adopted) younger than 18 years of age. Parents are categorized as “stay-at-home” based on their employment status during the year prior to the survey. This is generally similar to the approach adopted by the U.S. Census Bureau.

However, the Census Bureau limits the definition of stay-at-home parents to married people living with a child under the age of 15 who state that they were home for the entire year in order to care for home and family, as well as that they have an opposite-sex spouse who was in the labor force all year. The definition used here encompasses any parent of a child younger than 18 who has not worked for pay in the prior year, regardless of the reason, and regardless of their marital status or the employment status of their spouse or partner.

Determining an optimal definition of stay-at-home parents is difficult. For instance, excluding parents who are primary caregivers, but who also worked at least a few hours in the prior year, may lead to an underestimate of the actual number of stay-at-home fathers or mothers. On the other hand, some might argue that parents who are home due to an inability to find work should not be included as stay-at-home parents, even though they may be serving as the primary caregiver. See this qualitative analysis for additional insights on how caregiving fathers define themselves, and how various adjustments in the Census definition of stay-at-home fatherhood would affect national estimates of stay-at-home fathers.

Gretchen Livingston  is a former senior researcher focusing on fertility and family demographics at Pew Research Center.