Stars are enthusiastically taking on a new pledge to increase the number of female directors in Hollywood.

Time's Up and the Annenberg Inclusion Initiative recently announced a new challenge to members of Hollywood to commit to a project with one female director in the next 18 months.

The groups posed the challenge after finding that only 4% of the top 1,200 highest earning studio films were directed by women over the last decade.

The study also found that the ratio of male to female directors was 22:1 throughout the timespan.

Actress Tessa Thompson, who appeared on the "Making the (In)visible: Radical Transparency in the Data-Driven Age" panel at Sundance Film Festival, during which the challenge was announced, was one of the first stars to take the pledge.

“The 4% challenge is an important step forward towards achieving equity and improving representation in the entertainment industry and demonstrates the power of standing united in this fight," Nithya Raman, Executive Director of TIME’S UP Entertainment, said in a statement to ABC News.

"It is only by acting intentionally that we can create a world in which the stories that reach our screens better reflect the world we live in," the statement continued. "When we act collectively, we can change norms and make it unacceptable for such gross gender imbalances to continue, whether in the director's chair or across any position in this industry.”

"Crazy Rich Asians" producer Nina Jacobson, Angela Robinson, Franklin Leonard, Paul Feig and Amy Schumer were also among some of the earliest members of Hollywood to commit to the challenge.

Following their commitments and the release of the pledge, many actresses and actors followed suit and promised in social media posts to work on a project with one female director in the next 18 months, through social me.

Singer and actress Jennifer Lopez took to Twitter to announce she was on board, also mentioning her upcoming film.

"I officially accept the #4percentchallenge to announce a project with a female director on a feature film in the next 18 months," she wrote on the platform. "No better time to start than now with my new film #Hustlers directed by @lorenescafaria."

Actress Bryce Dallas Howard described that she was "sickened" by the statistics and urged people to take action.

"Time is waaaay up. As an actor and director, I am sickened by these statistics. This needs to change NOW. I officially accept the #4percentchallenge to work with other female directors on a feature film in the next 18 months. @timesupnow Who is in?" she wrote.

ReFrame, a group founded by Women In Film with the Sundance Institute to increase gender parity, also supports the new Time's Up challenge.

Amy Baer, Board President of Women In Film, Los Angeles, expressed her approval in a statement to ABC News.

"As an organization that has been fighting for female parity in the screen industries for over 45 years, Women In Film, Los Angeles is thrilled with TimesUp's 4% announcement and the enthusiasm with which it's been received," the statement reads.

"The only way we will accomplish our collective goals is by approaching this issue from all sides, within the traditional media structures and outside of them," the statement continued. Fieg, Leonard and Jacobson are also ReFrame ambassadors.

Showrunner Shonda Rhimes explained that most of her work revolves around television, as opposed to film, but is still supportive of the idea.

Other actors and actresses who have committed to honoring the pledge include Reese Witherspoon, Kerry Washington, Gina Rodriguez, Armie Hammer, Brie Larson, Constance Wu, Janet Mock, J.J. Abrams and Bad Robot and Jordan Peele.

The challenge supporting women in the film industry comes a month after Time's Up released a study examining top-grossing films in the U.S..

The study examined 350 films, released from January 2014 to December 2017, across all budgets, and found films with female leads outperformed male-led films.

Conducted by Los Angeles-based talent and sports agency Creative Artists Agency (CAA) and shift7, a technology company, the study categorized the pictures into five budget levels: under $10 million, $10 million to $30 million, $30 million to $50 million, $50 million to $100 million, and over $100 million.

Movies with female leads grossed more money in every category.