NEW YORK -- A new study finds that just 7 per cent of the 250 highest-grossing films of 2016 were directed by women.

The Center for the Study of Women in Television and Film at San Diego State University on Thursday issued the 19th annual edition of its report, titled "The Celluloid Ceiling," authored by the centre's executive director, Martha M. Lauzen. The rate of female directors was down 2 per cent from last year.

Despite widespread attention in recent years to gender inequality in the film industry, the study found not only that opportunities aren't improving, but are getting slightly worse. Nearly 20 years ago, in 1998, 9 per cent of the top films were directed by women.

Researchers found the disparity across the board. In 2016, women comprised 17 per cent of all directors, writers, producers, executive producers, editors and cinematographers in the top 250 domestic-grossing films. That also is a decline of 2 per cent from 2015.

In recent years, gender inequality in Hollywood has drawn increased scrutiny, including an ongoing investigation by the federal Equal Employment Opportunity Commission.

Numerous stars have also spoken out about pay disparity. Most recently, Natalie Portman, who last year released her directorial debut, "A Tale of Love and Darkness," told Marie Claire that she was paid three times less than co-star Ashton Kutcher in 2011's "No Strings Attached."

The centre's study also showed the trickle-down effect of hiring female directors. In analyzing the top 500 films, researchers found that on films with female directors, women accounted for 64 per cent of writers. On male-directed films, just 9 per cent were women.