The number of women working as both actresses in prime-time shows and writers and producers behind the scenes on those same shows fell in 2010-2011, a new study shows.

Just one in six writers on prime-time sitcoms, dramas, and reality TV shows were women, down from 29% in the 2009-10 season, according to the report from the Center for the Study of Women in Television and Film at San Diego State University.

One in four producers, directors, writers, editors and directors were women, and 41% of all on-screen characters were female, down from 43 percent the year before.

Only one network, CW, featured 52 percent female characters, representing women “in accurate proportion to their representation in the U.S. population.” The other broadcast networks’ shows had between 36 % and 43% female characters.

The study is based on surveying one randomly selected episode from each prime-time show, which the authors say should “minimize” sampling bias.

A separate study from the same center found that only 42 of 2010′s top 250 films had any women writers working on them; 98 percent of those films had no female cinematographers, and more than three-fourths had no women editors.