Yes it would be silly to treat something like sleepovers so seriously in themselves that the terms "birth" and "death" would be appropriate. However, they're part of the larger family of guest-host relations, which are central to a cohesive community and a meaningful life. So, as with the case of trick-or-treating, we can use sleepovers as a window into broader social life. Because it's costly to host your kid's friend during a sleepover, it's an honest signal of healthy guest-host relations, not just lip service.
Since the early '90s, play dates have taken over the social lives of children, and babysitters have disappeared as parents have lost trust in the outside world to take care of their kids. I looked for NYT articles specifically about the decline in sleepovers, but only found scattered remarks. In general it looks like fewer kids get to experience them, and even those that do at later ages, to fewer kids' houses, and with greater parental supervision. When I mentioned this topic to a woman with 2 young kids, she too said that sleepovers seem to have dwindled during the age of helicopter parents.
That's their end, but when did they get started? This graph shows how common the phrase "sleepover" is in Google's digital library across the pre-'90s period:
It moves steadily upward in the late 1950s, which a search of the NYT supports, and kept going through the '80s. We're most familiar with that from movies showing teenage sleepovers, such as Weird Science or any of the slasher movies. But anyone who was a child then will tell you that even elementary school kids had frequent sleepovers, across a pretty wide range of hosts, and that the parents generally stayed out of their way for the night.
So far we see the typical pattern of greater independence for young people, and stronger guest-host relations, during rising-crime times, and the opposite during falling-crime times. To really be sure, we'd want to see if that was true for the earlier 20th-C crime wave. Unfortunately the phrase "sleepover" doesn't go back that far, but as it turns out "slumber party" does:
It gets going around 1900 and peaks in the early-mid-'30s, right as the homicide rate peaks. It then plunges until the mid-'60s (although in the NYT it starts going up by the late '50s), and increases after that. So even during the earlier wave up and down of violence, slumber parties were part of wilder times and died out during safer times. You don't see a strong sleepover culture in A Christmas Story (set circa 1940) or in Mad Men (set circa 1960). In one episode Sally does get invited to sleep over at a friend's, but it's rare and only involves two kids, whereas when they were popular they'd sometimes include over a dozen guests.
I browsed through the actual books and magazines that these graphs are based on, from 1900 through the '30s, and the term meant exactly the same thing then as now. Most of the writings are for sorority newsletters and union bulletings, letting readers know what activities they'd hosted recently. Still there were other references to adolescents throwing slumber parties (such as the Camp Fire Girls and the Boy Scouts), and even small children. One referred to an 8 year-old girl inviting some school friends over for a birthday slumber party. As during the recent peak of this activity, it was not just restricted to young adults.
The phrase "pajama party" shows the same movement up and down as "slumber party," although it does get a later start in the late 1910s. Looking into the contexts, though, I found out that it didn't mean a sleepover or slumber party. Pajamas included a much broader range of clothes during the Jazz Age craze for pajama parties, and since most of them were held in a beach setting, I assume they featured "beach pajamas," which just look like wide-legged pants. It sounds like a way for the well-to-do to throw a party with a casual but sporty dress code. I didn't pick up any hint that sleeping over was involved, and it seemed like no one younger than 20 participated.
The take-home message here is that we've found another example of guest-host relations becoming stronger when people face a more dangerous world, and weaker when it gets safer. The logic behind it is pretty simple, but I'll save a summary for a later post, after looking at more examples. I'll also put it into a broader context of what types of societies rely heavily on such relations, and what types don't.