These are the top 3 most influential films and actors of all time, as per a study

The Wizard of Oz is the most influential film of all time, followed by Star Wars and Psycho, according to a study. Researchers at the University of Turin in Italy calculated an influence score for 47,000 films listed in the internet movie database(IMDb).

The score was based on how much each film had been referenced by subsequent films. The study, published in the journal Applied Network Science, found that the top 20 most influential films were all produced before 1980 and mostly in the US.

The Wizard of Oz is a 1939 American musical fantasy film.

"We propose an alternative method to box office takings -- which are affected by factors beyond the quality of the film such as advertising and distribution -- and reviews -- which are ultimately subjective -- for analysing the success of a film," said Livio Bioglio, the lead author of the study.

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"We have developed an algorithm that uses references between movies as a measure for success, and which can also be used to evaluate the career of directors, actors and actresses, by considering their participation in top-scoring movies," Bioglio said.

Applying the algorithm to directors, Alfred Hitchcock, Steven Spielberg and Stanley Kubrick ranked third, fifth and sixth respectively.

When the researchers used another approach to remove the bias of older movies --which, because they were produced earlier, can potentially influence a greater number of subsequent films -- Hitchcock, Spielberg and Brian De Palma occupied the top spots instead.

When applied to actors, the algorithm ranked Samuel L Jackson, Clint Eastwood and Tom Cruise as the top three.

The researchers noticed a strong gender bias towards male actors; the only female in the top ten was Lois Maxwell, who played the recurring role of Miss Moneypenny in the James Bond franchise.

"The scores of top-ranked actresses tend to be lower compared to their male colleagues,"  Bioglio said.

"The only exceptions were musical movies, where results show moderate gender equality, and movies produced in Sweden, where actresses ranked better compared to actors," Bioglio said.

To calculate the influence score for the 47,000 films investigated in this study, the researchers treated the films as nodes in a network and measured the number of connections each film has to other films and how influential the films connected to it are.

Similar methods have already been widely applied to measuring the impact of work in other fields, such as scientific publications.

"The idea of using network analysis for ranking films is not completely new, but to our knowledge this is the first study that uses these techniques to also rank personalities involved in film production," Bioglio said.

The researchers suggest that their method could be used for research in the arts and by film historians. However, they caution that the results can only be applied to Western cinema as the data on IMDb are strongly biased towards films produced in Western countries.