Online film piracy has little effect on weekend Hollywood box office sales, a study claims.

Reel Piracy: The Effect of Online Film Piracy on International Box Office, found that there was only a small drop in the number of people heading to the cinema despite the increase in piracy.

The study, carried out by researchers from Wellesley College, Massachusetts, the University of Minnesota and the National Bureau of Economic Research, found that the damage to a film's takings could be mitigated by reducing the gap between the US and worldwide release of a film.

Published at, the study found that on average a film lost around 7 percent of expected international cinema revenue due to piracy.

"Hollywood movies are typically first released in the US, then only later in France (say four weeks later), the UK (say eight weeks later) and so on. By the time a move typically arrives in Australian theatres, there is an abundant online supply," the study claims.

The study found that the widespread use of BitTorrent piracy software from 2003 had the most significant results. In 2003-04 an eight-week delay before widespread release would lead to an average on 22 percent losses, while in 2005-06 this could be as high as 40 percent.

Science fiction and action films took the biggest profits hit, losing around 1.3 percent more than other genres.

While the study saw no evidence of US weekend box office takings being significantly affected by online piracy, it saw a clear case that a delayed release outside the US drives losses to piracy.

The typical delay between a US and overseas release has declined year on year as distributors rush to maximise their takings. In 2004 the average window for release was around 10.5 weeks, which dropped to around four weeks in 2010.

"Studios should continue to reduce the length of the release lag, particularly for genres that are more heavily pirated such as science fiction and action films," the study concludes.