The obvious omission in this table is detective/mystery films, which would occupy a significant fraction of the overall whole, but IMDB, from which I took my data and which I admit is a flawed resource, breaks down such films into “crime” and “mystery,” with some overlap between the two, and I don’t have the time to parse out which films are truly mystery and which aren’t.
That said…
Drama: I’m surprised at drama’s decline. The 1920s were the years when the pulp market monolith fractured under the pressure of the genre pulps, until general pulps were of minimal interest and had minimal impact on the market. So too here, apparently–the rise in genre films in the 1920s in the 1920s matched and I think caused the decline in general-interest dramas, presaging the 1930s, in which genre films play such an important role in cinema as a whole.
Romance: I confess to being surprised at how small (comparatively speaking) romances were in the film market. I suspect–and I’ll eventually run the numbers for the 1930s–that in the 1930s romances are more important than they were before sound, most likely because romance films work better with sound than without. That said, romance’s peak (by percentage) is 1926, pre-Jazz Singer.
Science Fiction: Never a major part of film before the 1930s. But note the numbers during World War One! We need someone to take a look at these films and see how they compare to the fiction of the time. (My piece in the forthcoming Oxford Handbook of Science Fiction spends some time on the pulp fiction of those years).
Westerns: This is peculiar. Numerical peak in Westerns is 1912–in other words, before film had time to react to the popularity of Zane Grey’s Riders of the Purple Sage, which jumpstarted the Western genre in print. Over the next several years, as print Westerns became popular, film Westerns declined as a percentage of the market and in real numbers. Western films only increase in numbers starting in 1918 and then fluctuate, even while their percentage remains generally good. I suspect there’s a knock-on effect of the popularity of the Western pulps, but I can’t see a constant effect, much as I’d like to. And note 1929–romances are almost as much of the market as Westerns, for the first time.
Total: Criminy stevens, who’d have guessed film’s high point was 1915? And that the numbers of films made would decline almost interrupted after that? It will be interesting to see what the numbers are during the Depression.