Magic! Wizard of Oz is most inspiring film

The 1939 musical, starring Judy Garland, is famous for its early use of colour and the timeless song Over the Rainbow. It beats nearest rival Star Wars and Psycho in a league table of 47,000 films. Instead of looking at box office charts, researchers at Turin university in Italy calculated an “influence score” listed in the internet movie database (IMDb).

Each film was placed according to how often it was referenced by a later movie.

The top 20 most influential productions were all made before 1980, mostly by Hollywood.

A computer programme has measured how much of a connection the classics have to other influential films.

Lead researcher Dr Livio Bioglio said: “We propose an alternative method to box office takings, which are affected by factors beyond the quality of the film such as advertising, distribution and reviews, which are ultimately subjective, for analysing the success of a film.

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

Applying the same principle to actors, Samuel L Jackson, Clint Eastwood and Tom Cruise were ranked the top three.

The only woman in the top 10 was Lois Maxwell, who played Miss Moneypenny in James Bond films.

Dr Bioglio added: “The scores of top-ranked actresses tend to be lower compared to their male colleagues.”

But the researchers, whose findings are reported in the journal Applied Network Science, said that IMDb data was biased towards films produced in the West.

The Wizard of Oz, based on the L Frank Baum 1900 book, featured 16-year-old Judy Garland as Dorothy, Ray Bolger as the Scarecrow, Jack Haley as the Tin Man and Bert Lahr as the Cowardly Lion.