Saturday, 23 May 2009

Correlation of the Week: Zombies, Vampires, Democrats and Republicans

A friend of mine recently pointed me in the direction of an article in called With Obama election comes the return of the vampire. This article puts forward the theory that more vampire movies come out when Democrats are elected to the US Presidency, and more zombie movies come out when the Republicans are in office.

Recent evidence of this is the new Twilight vampire flick - coinciding with the election of Democrat Obama - and the spate of zombie films during George W. Bush's presidency - for example 28 Days Later, 28 Weeks Later and Dawn of the Dead. The original article looks back in time at various presidencies and it makes compelling reading.

What is the reason behind this (if there really is one)? One argument put forward is that the movies depict what we fear at the time.
Democrats, who believe in redistributing wealth among the people, fear the Wall Street vampires who bleed the nation dry. Vampires, such as Dracula, represent the aristocracy. Republicans fear a revolt of the poor and disenfranchised, and as such fear zombies.

But, is there any truth to this argument? Let's turn to the data. The easiest way to determine the number of vampire and zombie films which have come out over the last 50 years is to look at The Internet Movie Database. Using its power search, I was able to find the number of movies (not TV-movies , TV-shows or direct-to-video movies, but only big screen movies - imagine trying to quantify every TV-show ever made, not even imdb is that complete) made each year in the US since 1953 (a seemingly good point to start this analysis as there is plenty of data about the movies made in this time - it's also the presidency of Republican Dwight D. Eisenhower), as well as the number of movies tagged "vampire" and "zombie". You can see this data in the following table, where the year is the starting year of the presidency:

We've plotted the number of zombie and vampire films produced as a percentage of all films produced that presidential term in the US:

A stand out result is the large number of zombie films made in the 1980s under Reagan. It seems clear that zombie films peak in Republican years, but it is less clear whether vampire films have similar peaks under Democrats.

Indeed, the average percentage of movies that are zombie-themed produced during a Democratic presidency is 0.372%, whilst under the Republicans it is 0.571% - this is a large difference. The average percentage of movies that are vampire-themed produced during a Democratic presidency is 0.544%, whilst under the Republicans it is 0.491% - the percentage moves in the direction of our theory, but not by much.

Using a single-tailed Student's t-test (named after its inventor William Sealy Gosset, whose nom de plume was Student - I thought at school that it was named this because it was used by students, anyway...) to test between the null-hypothesis that the governing party makes no difference to the types of movies made and the theories that zombie movies go up under Republicans and vampire movies under Democrats, we find the t-statistic for the zombie case to be -1.69 which gives a p-value 5.7%. What this means is that there is a 5.7% chance that there is no significant difference between the zombie results under Democrats and Republicans. This is very close to the 5% level most statisticians accept for significance, and as such is a very intriguing result.

For the vampire case, our p-value is 33% and so there is little chance of significance. Both tests could be improved with more data (what every statistician needs!)

In summary, there just might be something in this (for the zombies anyway.) There is an almost significant difference between the percentage of zombie movies made under Democrats and Republicans. To predict the next election, it could well be worth looking at how many zombie movies are planned for the inauguration year and the 3 years after it. As most movies are planned more than a year ahead of time, this could be an interesting election predictor.

I guess we now know where George W. Bush's brains went! Brains.....