Found this interactive infographic from the New York Times. Using census data they created this to show the ways the American household is changing.
I think this will make researching family history more challenging in the future. It's so common to find leads and connections from census records in the past because the extended family often lived together or nearby. And with these large households they might have stayed put a little longer than the current households with individuals and locations changing yearly. I was so bummed after I filled out my first census record ever while I was living in New Jersey and then moved to Brooklyn a month later!