A U.S. movie industry marketing researcher says the number of sex scenes in movie scripts has been dropping over the past 18 months.

Vincent Bruzzese, president of the Ipsos company's movie research division, says movie executives are seeing a shift in the public's tastes.

"The number of sex scenes in the scripts we assess for our clients has absolutely declined in the last two years," Inside Movies quoted him saying.

"Writers are just leaving them out because they know they'll get cut. And when they are in the script, our clients want to know, 'Is this absolutely necessary?'"

Bruzzeses's company, Ipsos Worldwide Motion Picture Group provides consulting services to movie studios and filmmakers.

It helps evaluate and market films from the script stage, to audience screenings and for ways to adapt marketing campaigns based on audience feedback.

"Sex scenes used to be written, no matter the plot, to spice up a trailer.

"But all that does today is get a film an adult-only rating and lose a younger audience. Today such scenes are written out by producers before they are even shot," Bruzzese told the British newspaper, the Sunday Times.

"They ask: do we really need the sex? Can we fill the space with dazzling special effects instead and keep the family-friendly rating?"

The British Board of Film Classification has said that in Britain, the percentage of adult-only movies dropped from 12 percent in 2001 to 8 percent in 2011.

Another industry watcher say young people are finding more sex on the internet and television, according to the report.

"If the explicit sex scenes on TV shows such as Girls were made for cinema, they would get a certificate, which means newspapers would not advertise them nor would most cinemas show them.

"TV can go much further than mainstream Hollywood, which is relatively chaste these days," said Paul Degarabedian, president of the Hollywood.com Box Office division.