Source: Bureau of Labor Statistics
From the Summary:
In 2011, 11.5 percent of families included an unemployed person, falling from a peak of 12.4 percent in 2010, the U.S. Bureau of Labor Statistics reported today. Of the nation’s 78.4 million families, 79.8 percent had at least one employed member in 2011.
These data on employment, unemployment, and family relationships are collected as part of the Current Population Survey (CPS), a monthly sample survey of approximately 60,000 households. Families are classified either as married-couple families or as families maintained by women or men without spouses present. For further information about the CPS, see the Technical Note.