Zombie Movie production with regards to War and Social Upheaval

Interesting, and it's a huge list of movies they used. [Link]

Still, even correcting for the fact that there are more movies being made today, you can see that there are distinctive spikes in zombie popularity - and they always seem to fall slightly after a huge political or social event has caused mass fear, chaos, or suffering. That's why World War II, Vietnam, and the current Iraq War are all followed by a zombie rush at theaters. Obviously, if you're going to look at these historical correlations, you have to consider that movies inspired by a real-life event aren't going to show up in theaters for at least six months to a year, so we've accounted for that.

You can see that most of these spikes in zombie popularity do seem weirdly close to periods of historical trauma like wars or the AIDS epidemic. Is there a causal connection, or is it just coincidence? You be the judge.