Before the holiday, over at A World on Fire Brian blogged about the subject of the relationship of the zombie genre to periods of social dislocation in the United States. He approvingly linked to an older article at IO9.com that charted a correlation between the production of movies with a theme related to the living dead and periods of war and social upheaval. Check out each link for more of each of their respective takes.
Now that all the Turkey Day festivities are out of the way, I'd like to add a few words to what Brian had to say about this.
I think that the correlation that IO9.com found definitely exists - but only for a subsection of the genre. Periods of social upheaval contribute to the popularity of what you could call the zombie action genre, but do not necessarily contribute to the popularity of the zombie horror genre.
I think that to the extent the zombie genre is a subset of the horror genre, it would be hard to find a legitimate correlation. The production of horror films, and fashions within the production of horror films, is so deeply bound up with issues of film financing, film production codes, and the preferences of individual performers and directors that it would be hard to say, "These films were made because of the Viet Nam war," or "That set of films was the result of McCarthyism."
But not all zombie films [or stories in other media, which tend to track along with the fashions in film] can really be said to be part of the horror genre. Many of them - perhaps the majority now - are actually science-fiction action films or stories. Certainly films like 28 Days Later or Zach Snyder's version of Dawn of the Dead pretty clearly belong to the tradition of the science fiction disaster film more than they "fit" into horror. They're much more like Them or Day of the Triffids than they are like The Exorcist. I would argue that the appeal of these zombie action stories basically mirrors the appeal of the science fiction disaster film.
In her essay "The Imagination of Disaster", Susan Sontag outlined her view of the basic appeal of the science fiction disaster tale, and although I don't generally care for Sontag there's a lot in this particular essay to agree with. [Sorry, no link; I don't believe it's available online.]
The lure of such generalized disaster as a fantasy is that it releases one from normal obligations. The trump card of the end-of-the-world movies - like The Day the Earth Caught Fire (1962) - is that great scene with New York or London Or Tokyo discovered empty, its entire population annihilated. Or, as in The World, the Flesh, and the Devil (1957), the entire movie can be devoted to the fantasy of occupying the deserted metropolis and starting all over again, a world Robinson Crusoe...Another kind of satisfaction these films supply is extreme moral simplification - that is to say, a morally acceptable fantasy where one can give outlet to cruel or at least amoral feelings. In this respect, science fiction films partly overlap with horror films. This is the undeniable pleasure we derive from looking at freaks, beings excluded from the category of the human. The sense of superiority over the freak conjoined in varying proportions with the titillation of fear and aversion makes it possible for moral scruples to be lifted, for cruelty to be enjoyed.
In this respect, the zombie action story is like Sontag's model of a science fiction disaster film on steroids, with the amp turned up to eleven. How much of the appeal lies in the more or less openly conceded idea that fighting off a a zombie apocalypse would be fun? Many popular zombie-themed sites - like Zombie Squad or the Zombie Research Society - make no bones about the fact that they are primarily interested in what you could call the survival problem, which is basically the Robinson Crusoe fantasy in a modern context. Basically the subconscious psychological appeal Sontag claimed existed in some types of end-of-the-world sci-fi has been consciously brought out into the open in the zombie genre; we now openly admit that there is something cathartic and almost attractive about the idea that on the day after the zombie apocalypse, none of us will have to go to work, and everything in the malls and the gun stores will be free for the taking, and anyone who has become a zombie can be blown away at will. I don't think it's an accident that one of the largest zombie groups at Facebook is called "The Hardest Part of a Zombie Apocalypse Will Be Pretending I'm Not Excited".
To tie this in to what Brian and the IO9 folks were saying, if this is in fact the appeal of the zombie action story, then it makes sense that these types of stories would be more popular during periods when the population was frustrated or under great stress. When things are going well, fewer people are interested in the catharsis of a release from everyday obligations. When things are going poorly, the reverse will be true.
Of course, I need to cover this entire post with a great big Not That There's Anything Wrong With That. A lot of these "pop psychology" analyses can sound like they're critical of fans of the genre. Certainly Sontag intended to be critical, and patronizing. Not me, though. I've got my own bug-out plan and I own all these films and I sat down and chose to write my own zombie story - so all of these things apply to me, too. But it's OK. I've learned how to own it.