According to a recent report by the Census, married couples with children account for only 19.6% of all households in the U.S. The new figure represents a drop of 4.5 percentage points from 2000 when 24.1% of all households in the U.S. were married couples with children. The share of total households in 1970 was 40.3%.
As the share of households that include married couples with children decreased, one-person households and other household types rose. The share of one-person households increased from 17.1% in 1970 to 27.5% in 2012.
The dramatic decline in married households with children is due in part to delays in household formation. Researchers point out that Americans, on average, are waiting 5 years longer to get married when compared to 1970. Additionally, Americans are waiting longer to have children. The average age at first birth in 2006 was 25 compared to the average age at first birth age of 21 in 1970.
While delays in household formation place downward pressure on the demand for single-family homes, the increasing share of those living alone places an upward pressure on the demand for rental units. Trends in new multifamily construction suggest builders and developers may be taking delayed household formation into account. The share of multi-family homes built for rent increased from an historic low of 47% during the third quarter of 2005 to above 90% in 2013. Additionally, the size of units built for rent remains relatively small when compared to owner-occupied units. The median size of rental apartments was 1,081 square feet in 2012.
In fact, builder and developer sentiment about current conditions in the apartment and condominium market are at all time highs. In the second quarter of 2013, the Multifamily Production Index MPI increased nine points to 61. The (MPI) is measured on a scale of 0 to 100 so that any number over 50 indicates that more respondents report improving conditions than worsening conditions.
Although builders and developers appear to be well positioned to take advantage of the trends in household formation, it is important to recognize that delayed household formation does not mean these household are not eventually formed. Instead, many individuals will eventually marry and have children or form other household types.
Other household types (family and nonfamily) increased from 12.3% in 1970 to 23.9% in 2012. Other family households include one-parent families, about half of all respondents in 2012, with the remainder being families that include an unmarried householder and relative(s). The share of households that include couples without children has been remarkably stable, near 30%.
Eye on Housing 
How does the impact of investors who rent these properties have on these figures? Back in 1970, there weren’t a lot of benefits to rent properties.
The best way of thinking about this is to separate supply and demand. The increased presence of investors represents an increase in supply for rental properties. But over the long run, housing supply is fairly elastic (meaning a flat supply curve that can add new housing in responses to demand). This means that demand forces, like the count and type of households, dominate over the long-run. In the short-run, housing supply is inelastic, so the increased presence of investors reduces rents and results in an increase in quantity demand for rental housing. At the margin, this might delay home ownership among married couples.
[…] via NAHB. […]
Could it be that there is a factor missing that could be determined by looking at the data differently?
If you add three columns; married with children, living alone and other in 1970 you get 69.7 and if you do the same for 2012 you get 71. this may be due to the fact that immigrant families are sharing housing in a less traditional way by having more family members living in the household. Children, grandchildren and others.
This would certainly have an impact on how the numbers shake out.
In adding together married with children, living alone, and other you are left with household that are comprised of married couples without children. As suggested, the share of households that include married couples without children has been remarkably stable from 1970 to 2012, between 28% and 30%.
The share of the remaining categories (married with children, living alone, and other) have changed dramatically over the period
Immigrants are included by the Census in these estimates. If the head of the household is an immigrant married and children are present, the household type is listed as married with children regardless of whether other relatives live in the household. If the head of the household is an immigrant not married living with others, the household type is listed as other.
[…] changing nature of the American family is also noted in Census data that shows the share of total households defined as married couples with children has declined dramatically in …. In 1970, the share of the population in these traditional households was more than 40%; in 2012 it […]