It analyzed the box office numbers of 1,615 films that opened between 1990 and 2013, and whether the films passed the "Bechdel test". This is a test created by cartoonist Alison Bechdel in a 1985 comic strip. The movies have to include at least two named female characters, who have to have a conversation with each other that isn't about a male character. Movies that pass the test have a lower median budget than all of the films so they actually make more money than those that fail.
Walt Hickey wrote: "The total median gross return on investment for a film that passed the Bechdel test was $2.68 for each dollar spent. The total median gross return on investment for films that failed was only $2.45 for each dollar spent. And while this might be a side effect of films with lower budgets tending to have higher returns on investment than films with higher budgets, it's still a strong indicator that films with women in somewhat prominent roles are performing well."
The films that passed the test are lower than half. Recent films that pass the test include Frozen and The Hunger Games: Catching Fire. The films also performed well internationally, as movies that pass the test "still have comparable returns on investment."
This follows a study by San Diego State film professor Martha Lauzen that found few female characters in movies. Among the top 100 grossing films of last year, 15% of protagonists, 29% of major characters and 30% of all speaking characters were female.