NEW YORK—Women made up just 18 percent of all the directors, writers, producers, executive producers, editors and cinematographers who worked on the top 250 American films released last year, according to a new study.

The 20th annual “Celluloid Ceiling” study on the behind-the-camera employment of women was released Monday by San Diego State University’s Center for the Study of Women in Television and Film. The results show virtually no change in the last 20 years for women in Hollywood. In 1998, the same calculation of behind-the-scenes jobs for women was 17 percent.

The study found that in last year’s top 250 films, 25 percent of producers were women, 11 percent of directors were women and just 4 percent of cinematographers were women.

“The film industry has utterly failed to address the continuing underemployment of women behind the scenes,” said Martha M. Lauzen, the study’s author. “This negligence has produced a toxic culture that supported the recent sexual harassment scandals and truncates so many women’s careers.”

Last week, a study published by the University of Southern California Annenberg found that among the top 100 films at the box office, the percentage of female directors rose from 4.2 percent in 2016 to 7.3 percent in 2017. But that number was still less than the 8 percent in 2008.

As they have in the past, the studies give statistical evidence to the widespread alarm about gender equality in Hollywood. More than 300 women in entertainment recently formed the initiative Time’s Up to push for equal female representation among executives and to help sexual harassment victims defend themselves.