I constructed the following graph with the aid of Advance Title Search at IMDb.
How would you explain the shifting popularity of the three genres? Here are my thoughts:
The rising popularity of comedies in the 1930s and 1940s can be attributed to the tensions of the Great Depression and World War II. The renewed and rising popularity of comedies in the 1960s to 2010s can be attributed to the rising social tensions of those decades. The relative unpopularity of comedy in the 1950s attests to the “normalcy” of that decade.
There were a few silent “musicals,” but real musicals didn’t arrive on the scene until the late 1920s, so the rise in popularity in the 1930s is unsurprising. The further rise in the 1940s is probably the due to the impetus of World War II, and the need for “light” escape. The decline in the relative popularity of musicals since the 1940s reflects the growing “sophistication” of the populace. Musicals defy belief in ways that comedies and horror films do not. People often crack jokes; horror simply exaggerated the brutal reality of twisted bodies, twisted minds, and the destructiveness of man and nature. But people don’t begin a sentence and then break into song, with the backing of a full orchestra and the accompaniment of choruses and dancers.
What about horror films, the taste for which seems to have risen through the 1980s, dropped in the 1990s, and since resumed its climb? Viewing a horror film is a way of fighting fire with fire: immersing oneself in the phony frights of the screen in order to make the traumas of everyday life seem milder by comparison. The Great Depression was followed in turn by World War II and the Cold War that ended in 1991 (and during which nuclear annihilation seemed a possibility). The Cold War was studded with lesser but controversial wars (Korea, Vietnam), assassinations, social unrest, and oil shortages, to name some of the lowlights of the post-World War II era through 1991. Then came the “peace dividend” of the 1990s: a decade of 1950-ish “normalcy” (compared with what had preceded it). That brief era ended shockingly on September 11, 2001, and it has been followed by wars, seemingly unextinguishable terror, and economic stagnation (punctuated by the worst recession since the Great Depression). So moviegoers resumed their antidotal intake of horror.