Two major transitions in U.S. household structure involving the living arrangements of the elderly have taken place over the last two centuries. The first transition, around 1820, marked the demise of the colonial household economy and the rise of a privatized household economy (Degler 1980; Demos 1986; Lasch 1977; Ruggles 1987; Rutman 1977; Ryan 1981). The old tended to share households with the nonold after this time, and the prevalence of coresidence peaked at the turn of the twentieth century (Ruggles 1987). The second shift, around the late 1940s, marked a quiet “demographic revolution” in living arrangements (Smith 1986). It brought a rapid decline in intergenerational coresidence and a parallel rise in young adults and the elderly living as primary individuals.