Kathryn Bigelow's best director Oscar for The Hurt Locker in 2010 was hailed as a breakthrough, but the number of women working on Hollywood films, including directors, writers, producers, editors and cinematographers, remains stubbornly low, according to a report published this week.

The annual Celluloid Ceiling report shows that just 16% of behind-the-scenes personnel on the 250 highest-grossing films of 2013 were women, down from 18% in 2012.

To underscore how little progress there has been, in 1998 – the first year the Celluloid Ceiling report appeared – the figure was 17%.

Martha Lauzen, executive director of the Centre for the Study of Women in Television and Film at San Diego State University, which compiles the report, said: "The film industry is in a state of gender inertia. There is no evidence to suggest that women's employment has improved in key behind-the-scenes roles over the last 16 years."

According to the figures, 6% of the directors of the top 250 films in 2013 are women, a 3% drop from 2012 (and also from 1998). The drop is even sharper in the writing department: only 10% are women (down from 15% last year).

Arguably the most prosperous area for women in the film industry is in producer roles: they comprise some 25% in the top 250 films. This is the same percentage as last year, and represents a small 1% rise on 1998. However another department traditionally open to women – editing – has seen a drop, with 17% of films employing female editors this year as opposed to 20% last year.

Only 3% of cinematographers in 2013 were women (up 1% from the year before), while roles such as sound designers, visual effects supervisors and special effects supervisors all recorded 5% or less.

The fact that the proportion of women working in the film industry has barely changed over more than a decade is particularly concerning given the increasingly vocal campaigns around the issue. "People expected Bigelow's Oscar to have a halo effect on other women," Lauzen said. "It was a bit of wishful thinking. Attitudes remain a major stumbling block. There are some harsh realities women in the film community are facing."