(Bloomberg) — Hollywood churns out superhero films dominated by male characters, but winning over young women can be key to success at the box office.

U.S. female filmgoers ages 15 to 24 account for 2 million admissions a week, compared with 1.7 million for their male counterparts, according to a study by Webedia Movies Pro and Vertigo Research. Cinephiles over the age of 50 also are an outsized force at the box office, despite blockbuster movies generally targeting the young, the report found.

The results suggest that Hollywood could generate more revenue by better serving these groups, said Marine Suttle, Webedia’s chief product officer. Already, the industry has made progress: Walt Disney Co.’s “Captain Marvel” and “Dark Phoenix” have put female protagonists at the center of superhero stories this year. But a disproportionate share of speaking roles still go to men.

“Diversity in the cast is what is going to bring diversity in the auditorium,” Suttle said in an interview.

In the top 30 films surveyed between March 2018 and February of this year, 30% of casts were female. But films with a higher percentage of female characters drew more women to theaters. Movies with a majority of women in the audience had an average 45% female representation in the cast. A similar correlation was found in moviegoers above the age of 50, according to the study.

Still, it’s hard to determine trends because this was the first year the researchers did the study.

‘Book Club’

Last year’s “Book Club,” which starred Jane Fonda and Diane Keaton, was one example of successfully tapping older viewers. It exceeded revenue expectations by drawing an audience that was 80% female and 60% over the age of 50, according to Box Office Mojo.

Groups like the Annenberg Inclusion Initiative have been tracking the level of gender and racial diversity in Hollywood. The latest study by the group showed an increase in women on screen, with 40 of the 100 top films in 2018 featuring a female lead or co-lead. Only 11 featured female actors over age 45, but that was more than double the number the year prior.

As studios consolidate and potentially make fewer movies, the companies that remain will need to make films that attract all audiences, Suttle said.