This year, 80% of the nominees in the best actor category play roles based on the lives of actual people. The favorite is Leonardo DiCaprio for his Hugh Glass in The Revenant .

Eddie Redmayne won the Oscar last year for his role as Stephen Hawking in the movie The Theory of Everything .

Sixty percent of the nominations in the nineties were for roles based on real people: Geoffrey Rush won an Oscar for his turn as pianist David Helfgott in Shine .

Fictional characters dominated the seventies. George C. Scott's role as General Patton was the exception. Although Scott rejected the nomination, he won the award.

Most nominees for roles based on real people in the 1960s were historical figures. This image shows Katharine Hepburn as Eleanor of Aquitaine in The Lion in Winter .

In only two of the past 50 years—1976 and 1979—did all the nominees play fictional characters.

Four out of five of the nominees for Best Actor at this Sunday’s Academy Awards have something in common. Yes, they’re all white (and so is the fifth). They’re also all nominated for playing real people.

Over the past 50 years, roughly a third of the Oscars for Best Actor and Best Actress have been awarded for roles based on real people. Recently, those numbers have shot up: Since 2003, over half of the Best Actress winners and more than two-thirds of the Best Actor winners have portrayed characters who exist outside of movies.

You Sound Just Like Him

Biopics are as old as movies themselves. But while today’s actors tend to win awards for their realistic portrayals of historical figures, that wasn’t always the case. The studios who made biopics before the 1990s weren’t always interested in making an actor or actress look and sound just like the real person they were portraying.

In 1971, actor George C. Scott won (and rejected) an Oscar for portraying General George S. Patton, Jr. in Patton. In the film, Scott spoke with his trademark deep, gravely voice. But that wasn’t what the real Patton sounded like.

View Images In The Revenant, Leonardo Dicaprio plays real-life explorer Hugh Glass. The performance has fueled rumors that Dicaprio is “desperate” to win an Oscar. Photograph by Atlaspix, Alamy

“Patton spoke in a very high-pitched voice, and also a voice that told that he was from the upper classes of America,” says Dennis Bingham, author of Whose Lives Are They Anyway? Scott developed his own Patton-like voice, but “the studio wouldn’t let him use it. They thought it just sounded too strange, and went against the idea of what a commanding general would sound like—which is interesting, because that’s the reality.”

Today, the standards have flipped. In interviews for Lincoln, Daniel Day-Lewis described how he researched the way that President Lincoln probably talked, and developed his voice for the role based on that research. When Meryl Streep played Prime Minister Thatcher in The Iron Lady, audiences marveled at how she matched the politician’s voice and appearance.

Down to the makeup, the hair, the walk, and the talk, audiences have come to expect that actors and actresses embody their real-life characters as completely as possible. And Academy Awards voters are likely swayed by the lengths that these performers go to when deciding who should win the biggest acting awards of the year.

View Images In The Iron Lady, Meryl Streep played British Prime Minister Margaret Thatcher. She won the Best Actress Oscar for the role in 2012. Photograph by A.F. Archive, Alamy

Famous People Playing Famous People

What’s better than putting a famous actor in a movie? For studios, it’s having that famous actor play a famous person. Since 2003, 14 of the 16 real characters that won someone a Best Actor or Best Actress Oscar were already known for their political leadership, artistic or scientific accomplishments, or high-profile murder trial.

“I think that increasingly, there’s a move to reducing risk when producing in Hollywood studios,” says Belén Vidal, co-editor of The Biopic in Contemporary Film Culture. “So that means that something like a biopic of a famous personality, especially if there’s a pre-existing book or new story, is seen as more of a safe investment.” If the audience already knows the performer and the historical character, the studio feels more certain that “there’s an audience for it.”

Not all of the real-life characters that actors and actresses win awards for are well-known (Matthew McConaughey’s 2014 win for playing Ron Woodroof is a notable exception). But if you look at the last several Best Actor and Best Actress winners—Jamie Foxx as Ray Charles, Reese Witherspoon as June Carter—most of them are.

“Luckily or unluckily,” Vidal says, actors who play real characters “have more of an obvious effort in performance” than those playing fictional roles for which there is no public image to imitate. More and more, the ability of a famous actor to make themselves look and sound like another famous person “is acknowledged and rewarded at the Oscars.”

View Images Many people were upset that David Oyelowo wasn’t nominated for a Best Actor Oscar for his portrayal of Martin Luther King, Jr. in 2014’s Selma. Photograph by Pictoral Press Ltd, Alamy

Diversity at the Oscars

Or at least, it’s acknowledged in some. Of the last seven Best Actors and Best Actresses who played real people, most of them were in the Actor category, and all of them were white. And the Oscars’ diversity issue may feed into the reliance on true stories for inspiration—and vice versa.

“The biopic traditionally has been very gender biased,” Vidal says. It’s “been about the great men of history, or the white great men.” This means that there are often fewer leading roles based on real people for anyone who isn’t a white man.

This year, the issue of diversity was popularized with the Twitter hashtag #OscarsSoWhite. The discussion concerned not just the availability of roles for non-white actors, both male and female, but also the recognition of those roles. Despite performances like David Oyelowo as Martin Luther King, Jr., Carmen Ejogo as Coretta Scott King, or Will Smith as Dr. Bennet Omalu, all of the Best Actor and Best Actress nominees in the past two years have been white. In the past 50 years, only two people of color—Forest Whitaker and Jamie Foxx—have won Oscars for playing characters based on real people.

There are plenty of non-white and/or female characters throughout history that could be the subjects of movies, but studios might be unwilling to make films about them if they don’t think that the public is familiar with the story. And it doesn’t help things if, when films like this do appear, the Oscars don’t recognize them at all.