In the United States today, adult children living at home, except out of necessity, is seen as something out of the ordinary (and typically as reflecting badly on the children). Yet in the past multigenerational households were common, even though homes themselves were often (much!) smaller. E.g., in Ray Bradbury's semi-autobiographical Dandelion Wine, set in the 1920s, Douglas Spaulding lives with his brother, parents, grandparents, great grandmother, and a renter. When and why did this change of attitudes take place? (Note that I am asking specifically about the US; I'm aware that other cultures have radically different ideas about what kinds of households are "normal".)
This article describes the rise of the nuclear family as a sociological concept if you have access to it: http://psycnet.apa.org/psycinfo/1980-05325-001
Of note: "This article ^(an ^article ^the ^author ^quotes ^in ^agreement) emphasizes that the family structure propounded in earlier sociological theorizing as the prevalent structure in western societies (the so- called nuclear system) is essentially a myth."
The concept of nuclear family is described in this article as arising from the work of sociologists in the 1950s who described families as, "atomistic" and isolated functional units. And additional research in the 1970s described the surrender of family functions, education, healthcare, religious education, etc. to the society at large.
The article goes on to describe research where families aren't functionally nuclear because, for example, research in the 60s had 1/3rd of participants seeing extending family at least weekly. Additionally the main arguments for the nuclear family, age separation and extended distance, are mitigated by the presence of the telephone and result in families that aren't truly nuclear in the classical sense of the word as isolated family units.
The author argues that it was industrialization that led to the myth of the nuclear family because people wanted to place their separation from family in a new framework that saw separation as promoting industrial progress but also that the nuclear family as an ideal is a myth that has never been realized. (this can be seen in the data at the end of this post where at least 12% of people have lived in multi-generational homes)
This paper is against the nuclear family as a sociological concept so perhaps it's a bit biased, but it's quite the interesting read because it's so different from our normal conception of family as we get taught in american history. It presents the nuclear family as an unrealized cultural ideal that primarily arose from the work of sociologists in the 50s/60s.
It's also interesting to note that recently almost 16%, a rising share, of people live in multi-generational households and that the research that described the nuclear family as a concept took place at the very low point of this trend.
http://www.pewsocialtrends.org/2010/03/18/the-return-of-the-multi-generational-family-household/
edit: TL;DR The nuclear family never existed, it's an invention of the sociologists of the mid 1960s, primarily Laslett at cambridge
Edit: This also isn't to say that the extended family is the best way of describing families. sociological research into the nature of families continues. Perhaps this is best described by the rise of the "postmodern family" in the research of the early 90s: http://jfi.sagepub.com/content/14/1/5.short
edit: as always psychological and sociological research is unduly focused on the West (which makes sense I suppose, funding for research and all that is done by rich countries)
Hope this is the right place to ask: Does this trend coincide with the housing shortage/significant rise prices in cities like NYC and SF, or did that come later?