Male characters outnumbered their female counterparts by two to one in Hollywood's most successful films, research shows.

A report published in the journal 'Sex Roles', which has been authored by Conor Neville and Phyllis Anastasio of Saint Joseph's University, has underlined the extent of the gender gap in America's film industry, showing that a little over 32 percent of characters in 50 of America's top-grossing movies of 2016 were female.

However, a similar study in 2005 found that 28 percent of all characters and 27 percent of lead roles were filled by women, suggesting the overall landscape has marginally improved.

Neville explained: ''Progress has been made, but men still outnumber women two to one in film, which means that the more powerful representations of women seen in our sample are not getting the screen exposure comparable to their proportion in the real world.''

In recent years, a number of Hollywood's most high-profile female stars have bemoaned the lack of opportunities for women in the movie business.

But Shailene Woodley has praised Nicole Kidman and Reese Witherspoon for ''reshaping'' the entertainment industry.

The 26-year-old star worked with the Oscar-winning actresses on 'Big Little Lies' - which was developed and produced by the pair - and is grateful for what they have been doing to promote opportunities for women.

She said: ''They've reshaped the industry for women and continue to do so, so that actors like myself and Zoe [Kravitz, her co-star] can have that liberty to express ourselves and thrive in an environment that doesn't class us as a minority or devalue our worth due to our gender.''

Despite this, Shailene believes there is still a long way to go and that true equality will only have been achieved when gender stops being a point of reference.

She added: ''We need to stop referencing gender entirely.

'''Big Little Lies' was referred to as a 'show led by five women'. When do we ever say, 'Wow! A show led by five men, that's amazing'?

''It describes the standard and level we're still at and I want to work towards a moment when we never think to question or advertise such a thing.

''I want it to be the norm and it will be the norm - but there's a way to go.''