	Distribution of Children under 18 by type of households relationships

	1940	1960	1970	1980	1990	1996	2003
Two parents	85.1	87.2	82.8	76.9		68.01	68.67
One parent	9.9	9.2	13.7	19.3		27.86	27.34
Neither parent	5	3.7	3.6	3.9		4.13	3.99
In group quarters	1	0.7	0.6	0.4		0.01

Note that the "group quarter" category disappears sometimes between 1996 and 2003.

Sources:

for 1940 to 1980 figures: American families and households (Sweet and Bumpass 1987)
for 1996: census report (p26)
for 2003: census report

May 2006 [1998 ]