Which family type is the fastest growing in the US? — Which family type is the fastest growing in the US?

Quick answer and what this article covers

Short takeaway

The clearest, short answer is that multigenerational households account for the largest absolute increase in recent decades, while categories that started small, such as same-sex couple households, can show the fastest percentage growth; readers should expect different answers depending on whether they look at absolute counts or percent changes, and the article below explains why and where to check the primary data. The future of american families is shaped by these definitional and measurement choices and by drivers such as housing and caregiving, according to public data from the U.S. Census Bureau and research centers like Pew and the Williams Institute U.S. Census Bureau

This short section describes what the rest of the article contains: definitions and measurement notes, a discussion of how analysts use absolute versus percentage change, a snapshot of national findings from the ACS and major research centers, and practical guidance on reading headlines and locating source tables.

How to read the rest of the article

Each major section below follows a consistent pattern: a short explanation, the relevant data source or study, and caveats about interpretation. When a specific growth claim is made, the paragraph links to a primary source so readers can check the tables themselves Pew Research Center

The article uses American Community Survey and Census family tables where possible, and it notes where specialized estimates – for example of same-sex couple households – come from centers such as the Williams Institute Williams Institute

Key terms and definitions to know

What counts as a family or household in Census statistics

The Census Bureau distinguishes households from families: a household is anyone sharing housing and living arrangements, while a family household includes at least two people related by birth, marriage, or adoption, according to Census tables and ACS documentation U.S. Census Bureau

Multigenerational households are typically identified in Census and ACS tables as households that include more than two adult generations or a grandparent and grandchild under one roof, depending on the table construction; those counts are visible in ACS household and family table series ACS 1-year estimates

In this article, multigenerational households refers to households where more than two adult generations live together or where grandparents and grandchildren co-reside; cohabiting households refers to unmarried partners sharing a household and identified in ACS partner categories; same-sex couple households means households where the partnered adults are recorded as the same gender; single-parent households means family households headed by one parent with children, as classified in ACS family tables ACS 1-year estimates

Survey measurement matters: identifying cohabiting partners or same-sex couples depends on how questions are asked and on respondents reporting partnership, so comparisons across time or across surveys require care and consistent series such as the ACS or CPS/ASEC Williams Institute

How researchers measure ‘fastest growing’ and why it matters

Absolute change versus percentage growth

When analysts ask which family type is “fastest growing,” they must choose a metric: absolute change measures how many more households of a type exist now versus before, while percentage growth measures the proportional increase from the earlier number; absolute increases tend to favor larger-base categories such as multigenerational households, while percentage growth can be largest for small-base categories like same-sex couple households U.S. Census Bureau

The choice of time window matters because short periods can amplify temporary shifts, while longer windows smooth volatility; consistent time series such as ACS or CPS are needed to make reliable comparisons across years Williams Institute

Time windows, base rates, and survey comparability

Base rates affect interpretation: a 50 percent increase on a category that started with a small number may still be a smaller absolute change than a 10 percent increase on a much larger category; analysts caution that percent-change headlines can mislead without the base size reported Williams Institute

Survey comparability is another concern. Changes in question wording, classification of partners, or improvements in enumerating households can produce apparent growth that partly reflects measurement change rather than only demographic shifts, according to Census analysts U.S. Census Bureau

National data snapshot: what Census and major centers report

Recent ACS and Census headline findings

Public ACS and Census tabulations show that multigenerational households rose substantially over recent decades and accounted for a larger share of the population by 2021 than in 1971, a pattern visible in Census family tables and ACS series U.S. Census Bureau. Harvard JCHS projections

ACS estimates also document steady increases in cohabiting households since 2000, and the ACS 1-year tables provide current shares and counts for unmarried-partner households ACS 1-year estimates

What Pew, Brookings and Demography add

Pew Research Center has emphasized the scale and drivers of multigenerational household growth, linking the pattern to economic and demographic forces in a multi-year analysis Pew Research Center

Brookings provides analysis of where multigenerational increases are concentrated and highlights factors such as housing affordability and immigration that shape regional patterns Brookings Institution

Academic work in Demography and other journals places these trends in longer-term context and offers caution on measurement and subgroup patterns, especially where specialized estimates are required Demography

Main drivers: why family arrangements are changing

Housing costs and affordability

Analysts consistently list housing costs and affordability as a primary driver of increased multigenerational co-residence; when home prices or rents rise faster than incomes, families sometimes combine households to share housing costs, a pattern noted in Pew and Brookings analyses Pew Research Center

Other economic shocks, labor-market changes, and demographic shifts can also push households toward shared living arrangements for financial resilience Brookings Institution

Demographic, immigration and caregiving factors

Demographic change and immigration can increase multigenerational households when immigrant families bring cultural norms of extended family living or when younger adults and older relatives share housing for mutual support; caregiving needs for older adults are another commonly cited reason for more multigenerational households Pew Research Center

Care needs and age-structure shifts also interact with housing and economic conditions to shape where and how quickly certain household types grow Brookings Institution

Deep dive: multigenerational households and why they stand out

Magnitude and recent absolute growth

Multigenerational households stand out because their absolute increase is large in recent decades, adding many more households in raw numbers than some other categories; Census tables and Pew analysis document the scale of that rise through counts and shares over time Pew Research Center

Regional and subgroup patterns

Increases in multigenerational living are not evenly distributed. Analysts find concentrations in certain metropolitan areas and among immigrant communities, as well as in regions where housing costs are high relative to incomes Brookings Institution and recent housing-trends analysis from the Boston Fed

For readers interested in local patterns, ACS 1-year tables provide state and metro-level breakdowns that show where absolute increases are largest, and those tables are useful for follow-up research ACS 1-year estimates

Comparing same-sex, cohabiting and single-parent households

Same-sex couple household percentage growth versus scale

Same-sex couple households have recorded some of the fastest percentage growth from a small base in recent decades, though they remain a relatively small share of all households; specialized estimates and commentary from the Williams Institute help explain both the growth rate and the remaining scale of that population Williams Institute

Because same-sex couple counts begin from a smaller baseline than multigenerational households, percent-change comparisons alone can exaggerate the practical scale of change unless the base size is also reported Williams Institute

Cohabitation trends since 2000 and single-parent stability

Cohabiting, unmarried-partner households have increased steadily since 2000 and now make up a larger fraction of partnered households in ACS and Census tabulations, reflecting both social change and changing partnership patterns U.S. Census Bureau

Single-parent family households have shown only modest short-term changes in recent years but continue to represent an important segment of family households in ACS estimates ACS 1-year estimates

Common pitfalls, data limitations and how to read headlines

Misleading use of percentage change on small bases

Headlines that report the largest percentage gain without showing the starting number can mislead readers; always look for the base count and the time window to understand whether a large percent increase actually represents a large absolute change Williams Institute

Survey undercount, question wording changes, and classification shifts can all affect reported trends; where possible, compare consistent series such as ACS 1-year tables or CPS series and note any methodological changes documented by the data source U.S. Census Bureau

Practical checklist for readers

When evaluating a headline, check the metric, the source, the time window, and whether the report gives both base counts and percentage changes, and consult the original ACS or Census table if available ACS 1-year estimates

For demographic impact, absolute change is often more informative; for proportional change among small groups, percent growth can matter; choose the metric that matches your question about policy, population impact, or representation U.S. Census Bureau

Practical takeaways and where to find the source data

Top three reader takeaways

Multigenerational households have had the largest absolute increases in recent decades, a fact visible in Census family tables and Pew analysis Pew Research Center (see also USA Today)

Same-sex couple households can show the fastest percentage growth but still represent a small share of all households, as described by specialized estimates from the Williams Institute Williams Institute. See author background on About.

Cohabiting households have grown steadily since 2000, and single-parent households remain a stable but significant portion of family households, all visible in ACS and Census tables ACS 1-year estimates

Links to Census tables and research reports to consult

For the most current figures, consult ACS 1-year tables and the Census family tables, and review research summaries from Pew, Brookings, and the Williams Institute for interpretation and subgroup analysis U.S. Census Bureau, and related posts on Michael Carbonara.

Remember to check the latest ACS or CPS releases for one-year updates and state-level breakdowns if you need recent or local estimates ACS 1-year estimates