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Human Population Dynamics

How Family Structure has Changed

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Data about family structure illustrate how individuals in an area are organized into different family arrangements.

What is a Family?

According to the U.S. Census Bureau, a family is "a group of two or more people who reside together and who are related by birth, marriage, or adoption" (U.S. Census Bureau). Though this definition seems straightforward, where do married couples or parents and children who live in different places fit in this definition of family? What about aunts and uncles who regularly care for their nieces or nephews while the parents work? According to the Census Bureau's definition, these relatively common family arrangements are not officially recognized as families. While the Bureau's definition of families is clear and is easily tracked over time, it is important to recognize that not all of our families fit this definition.

In fact, across time and cultures, using the Census Bureau definition of family is an inappropriate way to measure and examine families. In ancient Greece and in feudal Europe, a family was all of the people who contributed to the household financial system, including servants (Coltrane and Collins, 2001). In many cultures today, non-parental adults are also considered part of the family if they play a large role in raising or looking after the children of others. These examples highlight the fact that, though the Census definition is clear and helpful, there is no single understanding of what a family is; its definition varies across many groups of people.

How Have Families Changed over Time, and Why?

The structures, or forms, of the family vary as much as the definition itself. There is no single "true" family form. In Western Europe the nuclear family (a single set of biological parents residing together with their children) was prevalent in the Middle Ages, but at that same time in Eastern Europe multiple generations of the same family lived together in the same household (Coltrane and Collins, 2001). Indeed, the United States has also seen many types of family forms throughout its short history. Stephanie Coontz's (2005) research on the history of marriage reveals that the family forms we see today in the U.S. are actually the result of an evolution of the family that began with an important shift in the culture of marriage in the mid-18th Century.

A Family at the Beach

A Family at the Beach
Microsoft Office Online Clip Art

Coontz (2005) found that only in the mid- to late-18th Century in Western Europe and North America "did the notion of free choice and marriage for love triumph as a cultural ideal...[opening] the way for it to become an optional and fragile [institution]" thus influencing the structure of the family at that time and into the future (p. 7). Earlier in history, during the Stone and Middle Ages, marriage was not based on love and men and women had very little choice about whom they married. In the Stone Age men and women married in order to improve the economic situation of their respective clans, then in the Middle Ages and into the 18th Century marriage served the economic and political needs of a particular extended family group (Coontz, 2005).

As marriage evolved in the mid- to late-18th Century into a union based on love, other economic, cultural, and political shifts in the U.S. and in other nations were happening that would further influence the structure of the family. In the 19th Century an ideal of the husband as breadwinner and the wife as homemaker became popular, but the majority of families could not achieve this ideal, as few jobs paid wages high enough to support a single-earner family. This changed as World War II ended and the U.S. experienced a time of dramatic economic growth. The economic prosperity of the time combined with the popular cultural ideal gave rise to family trends in the 1950s and early 1960s that had never been seen before. "Ozzie and Harriet" families that married young, remained married, and had many children were the major family form at this time (McLanahan and Casper, 2001). The realization of the Ozzie and Harriet ideal did not last long, however. In the late 1960s and 1970s divorce rates rose, births to unmarried women increased, and the average age of first marriage also rose. The reasons for these changes in the '60s and '70s were many: real wages for women rose while those for men fell, the economy weakened, wives joined the workforce due to the downturn in the economy, and women gained access to legal rights, education, birth control, and paid work (McLanahan and Casper, 2001; Coltrane and Collins, 2001). This historical examination of the evolution of the family and marriage shows that the family has constantly been under pressure to evolve and shift with changes in the economy, our values, and even politics. The evolution of marriage into an institution of love along with changes in the economy, our culture, and the political scene since the 1950s has meant that American men and women have been able to realize their ideals of the male breadwinner and marriage for the sake of love and personal freedom as time changes.

These influences and trends in marriage, divorce, and non-marital fertility did not escape rural America. Comparing urban and rural parts of the country between 1950 and 1970 reveals, however, that rural divorce rates were lower, fewer women age 20-24 were unmarried, and the number of children per 1,000 ever married women age 35-44 was slightly higher in rural America (Brown, 1981). The changes in marriage, divorce, and fertility we observe during the 20th Century in all parts of the U.S. demonstrate that the structure of families are changing and becoming more diverse. While there are now many forms available to people, the family itself is not disappearing.

Why Do Families Matter?

The increasing diversity of the family in the U.S. has led scholars to examine if and how different family forms are associated with different groups of people who then may experience different outcomes. Research has found that not all racial groups participate in each family type equally, thus not all family forms are equally available to all people (McLanahan and Casper, 2001). Scholars have also found that each type of family (e.g., married with kids, married with no kids, single-parent with young children, etc.) is associated with different economic, child, and health outcomes. Demographers Sara McLanahan and Lynne Casper (2001) explain that past research has found that:

Children who grow up with only one of their parents"¦are more likely to drop out of high school, to become teenage and single mothers, and to have trouble finding and keeping a steady job in young adulthood, even after adjusting for differences in parents' socioeconomic background (McLanahan & Sandefur, 1994). (p. 6)

They clarify, however, that "about half of the disadvantages associated with single parenthood are due to lower incomes [of single parents]. Most of the rest are due to too little parental involvement and supervision and too much residential mobility" (p. 6). Stephanie Coontz (2005) also clarifies that the psychological, health, and economic benefits of marriage for families are due to a number of factors like: the effect of selection (people who are already healthier, more psychologically stable, and better able to manage finances tend to marry more than those who are not), the "expectations about responsibility, fidelity, and intimacy" in marriage, and the freedom to exit psychologically, physically, and economically stressful unhappy marriages (p. 309-310). While we see increasing diversity in family types in the U.S. across time it is clear that not all types lead to equal outcomes or are equally available to all.

Explore on Your Own!

Are there differences in family structures between urban and rural Oregon communities in 1990 and 2000? Did the prevalence of some family forms change in some places between 1990 and 2000? Are there communities with high rates of single parenthood? Why do you think they are high?

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Links to additional sources of information about family structure

National Survey of Families & Households, from University of Wisconsin-Madison Center for Demography and Ecology:, national indicators of child and family wellbeing from The Federal Interagency Forum on Child and Family Statistics:

Family Structure-Related Terms

Using the tools of the Oregon Communities Explorer you can examine family trends across the state among the following variables:

  • Average Family Size: The number of members of families divided by the total number of families, where a family is a group of two or more people who reside together and who are related by birth, marriage, or adoption.
    Formula: [# of all people in families]/[# of families]
    Source: US Census Bureau

  • Average Household Size: The number of people who share a housing unit as their usual place of residence divided by the total number of households.
    Formula: [# of all people in households]/[# of households]
    Source: US Census Bureau

  • Marital Status by Gender: The percentage of men and women over age 15 who either have never married, are currently married, are widowed, or are divorced.
    Formula example: ([# unmarried men]/[population of men age 15+])*100
    Source: US Census Bureau

  • Families with Children: The percentage of families that have children under 18 years old.
    Formula: (([# married-couples with children under 18]+[# single men with own children under 18]+[#single women with own children under 18])/[total # of families])*100
    Source: US Census Bureau

  • Single-parent Families: Of families with children, the percentage headed by a single parent, either male or female.
    Formula: (([# single men with own children under 18]+[# single women with own children under 18])/[total number of families with children under 18])*100
    Source: US Census Bureau

  • Teen Pregnancy Rate: Number of pregnancies per thousand teen females.
    Formula: ([number of pregnancies to females age 15-17]/[number of females age 15-17])*1000
    Source: Oregon Department of Human Services, Center for Health Statistics

  • Births to Unwed Mothers: The percent of live births that are to unmarried women.
    Formula: ([number of births to unwed women]/([number of births to unwed women]+[number of births to wed women]))*100
    Source: Oregon Department of Human Services, Center for Health Statistics


Coltrane, Scott and Randall Collins. 2001. Sociology of Marriage & the Family: Gender, Love, and Property. Fifth Edition. Belmont, CA: Wadsworth/Thomson Learning.

Coontz, Stephanie. 2005. Marriage, a History: From Obedience to Intimacy or How Love Conquered Marriage. New York, NY: Viking Penguin.

Brown, David L. 1981. A Quarter Century of Trends and Changes in the Demographic Structure of American Families. In Raymond T. Coward and William M. Smith Jr. (eds.), The Family in Rural Society. Boulder, CO: Westview Press. Pp. 9-26. 

U.S. Census Bureau. American FactFinder Glossary. Downloaded July 8, 2008. Technical Documentation: Census 2000 Summary File 1.

Authored by Lena Etuk, Social Demographer, Oregon State University Extension Service (2008)