Generations. The number of generations in a household is determined by the variable defining the relationship of each person in the household to the head. Each household has a “base” generation determined by the reference person or head of the household. Others in the base generation include the reference person’s spouse, siblings and siblings in law. Generations beyond this base are defined by individual relationships:
1. Base generation: reference person, spouse, sibling, sibling in law
2. Children (“-1” generation): child of head, child in law
3. Parents (“+1” generation): parent of head, parent in law
4. Grandchildren (“-2” generation): grandchild of head
5. Others: great-grandchild of head, grandparent of head
The datasets used for the analysis are from Decennial Censuses of 1900-2000 and the American Community Surveys of 2006-200925 as provided by the Integrated Public Use Microdata Series (IPUMS).The IPUMS are compiled by the University of Minnesota Population Center. Documentation is available at http://usa.ipums.org/usa/doc.shtml.
The IPUMS datasets permit determining generational composition for other types of relationships (e.g., aunt, uncle, niece, nephew) and for persons not related to the household head because the dataset identifies parental linkages where possible. So two generations are also present in a household if a person is determined to have a parent based on the IPUMS variables “MOMLOC” and “POPLOC.” If the parent also has a parent, a third generation is present.
Multi-generational Households. For our analyses, save for one exception, multi-generational households are defined as households with at least two generations of adults. The principal type of multi-generational household actually has two generations only—parent(s) and the adult child(ren):
a. Householder (and spouse), parent (or parent in law)
b. Householder (and spouse), adult child (or child in law)
In our analyses, we define adult children as those ages 25 and older rather than ages 18 and older. With this definition, the vast majority of college students living at home are not treated as an adult generation.
The next largest type of multi-generational household is the three generation household. There are a number of variants on this type, but the major ones differ as to whether the householder is in the middle generation (i.e., a “sandwich” household) or the older generation (i.e., a “grandparent” household):
a. Householder (and spouse), parent (or parent in law), child (or child in law)
b. Householder (and spouse), child (or child in law), grandchild
Note that in these households, the children do not have to be adults.
The only type of multi-generational household we define that does not necessarily include two adult generations is what might be called the “skipped” generation household. In these households, a grandchild is present but the grandchild’s parental generation is not present in the household (i.e., it is “skipped”). These multi-generational family households can be of two types:
a. Householder (and spouse), grandchild
b. Householder (and spouse), grandparent
Most households are not multi-generational households; they are single-generation households (the householder and possibly a spouse) or two-generation, adult-minor child households. In the early years of the 20th century, there were twice as many of these two generation households as one generation households. This pattern began to change in 1930 as one generation households increased in prevalence. By 1970, there were roughly equal numbers of the two households. In 2008, there were 70% more one generation than two generation households.
The definition of a multi-generational household used in this report is more expansive than the definition used by the Census Bureau. The Census Bureau defines multi-generational households as follows: A multi-generational household is one that contains three or more parent-child generations; for example, the householder, child of householder (biological, stepchild or adopted child), and grandchildren of householder. A householder with a parent or parent-in-law of the householder and a child of the householder may also be a multi-generational household (see page B-6 in: http://www.census.gov/prod/cen2010/doc/sf1.pdf).
According to the Census Bureau, 3.8% of U.S. households in 2010 were multi-generational (http://www.census.gov/newsroom/releases/pdf/acs_2010_highlights.pdf). The definition used in this report finds that 10.5% of all households in 2009 were multi-generational.