For the first time in 150 years, households headed by single adults and unmarried couples now outnumber married-couple families. In 1960, married-couple households represented more than 78 percent of American households. As late as 2000, married couples were 52 percent of all households. But in 2005, according to the recently released American Community Survey, households with a married couple at their core made up less than 50 percent of all households.