Nearly 80 percent of film critics are male, according to a new study that analyzed the movie reviews to last year's top box-office hits.

The research was conducted by the University of Southern California's Annenberg Inclusion Initiative, which released its findings Monday. Researchers studied the reviews of the 100 top-grossing films of 2017 that were posted on the aggregation website Rotten Tomatoes.

Of the 19,559 reviews studied, 77.8 were by male critics and 22.2 were by female critics. Stacy Smith, founder and director of the Inclusion Initiative, said film critics are "overwhelmingly white and male."

Female critics from minority groups accounted for just 4.1 percent of reviews studied. Smith urged "the publicity, marketing and distribution teams in moviemaking" to increase access and opportunity to women of color critics.