Why do so many foreign directors win Oscars?

Over the last 20 years, 11 winners of the best director Academy Award -- arguably second in prestige to best picture at Tinseltown's biggest annual show -- have been from outside the United States.

And if Mexican Alfonso Cuaron wins the coveted prize for space thriller "Gravity," as many predict, he will be the fourth non-American in a row to win in the category.

The same would be true for fellow frontrunner Steve McQueen, the British filmmaker behind "12 Years a Slave," a best picture frontrunner.

They would follow Briton Tom Hooper for "The King's Speech" in 2011, Frenchman Michel Hazanavicius for "The Artist" in 2012 and Taiwan-born Ang Lee for "Life of Pi" last year.

The success of foreign directors in Tinseltown is in fact nothing new -- it's been a constant since the 1920s, when Germans Ernst Lubitsch and F.W. Murnau settled in the United States.

"We've always had lots of British directors. Alfred Hitchcock is just one of many and there's always been an exchange between British cinema and American cinema," film historian Jonathan Kuntz told AFP.

"And then of course, depending on world circumstances, we had a lot of film makers driven to the US. Of course the Nazis drove most of the good filmmakers out of Europe."

Kuntz, an associate professor at the University of California Los Angeles (UCLA), added: "Then, Eastern Europe during the 60s and 70s -- a lot of filmmakers fled from there essentially, (Milos) Forman, (Roman) Polanski and many ended up in Hollywood."

But experts say the wave of foreign filmmakers pouring into Hollywood since the turn of the millennium is above all motivated by the changing economic model of movie studios.

"Fifty years ago, the industry was making roughly 70 percent of its revenue on domestic sales. Now, 80 percent is coming on foreign sales and only 20 percent is domestic sales," said history professor Steve Ross.

"So part of the reason, I think, they are going for foreign directors is also to appeal to their new base, who is a foreign base," the University of Southern California (USC) academic told AFP.

Laura Isabel Serna, assistant professor at USC's School of Cinematic Arts, added: "This is part of Hollywood's global marketing strategy that encourages audience identification with 'their' directors or actors.

"What is interesting is that, whereas in the past Hollywood has turned to Europe, studios are increasingly turning to other parts of the world as well, which is a testament to the vibrancy of film production in places like Latin America."

But while European, Asian or Latin American filmmakers are welcomed here for their "sensibility," studios don't want them to bring too much of their own national perspective to the screen.

"American directors know what American audiences want, but a foreign director coming in is going to have a sensibility that has to appeal to a larger audience," said Ross.

In most cases it works fine: "Gravity," written by Cuaron and his son Jonas, has made over $700 million at the global box office. His compatriot Guillermo Del Toro earned nearly $410 million last year with sci-fi blockbuster "Pacific Rim".

"Del Toro is an amazing guy," said Kuntz.

"He's Mexican through and through and at the same time he grew up on American pop culture, he's obsessed with it, clearly. He knows American pop culture better than almost any American.

"And the kind of filmmaking he does -- horror, science-fiction and genre -- that's something Hollywood loves also. He seems to fit right into the system."

Cuaron "is a great artist," he added. "This is one of the great cinema masters of the world right now. You have to admire his accomplishment."

Ultimately though, the only real common denominator between filmmakers who succeeded in Hollywood in cinema's golden age, the 1970s and those of the 21st century, is commercial success, said Ross.

"The bottom line in Hollywood is always the bottom line, the profit," he said, stressing: "The ultimate aim of the studios is to bring in personnel who can expand their markets and increase their profits."