Hollywood studios have claimed that film piracy cost them $6.1bn (£3.3bn) in lost revenue in 2005.
The study, commissioned by the Motion Picture Association of America (MPAA), suggested the figure was 75 per cent higher than previous estimates.
The report is the first to measure losses for internet piracy, which it said cost the industry $2.3bn.
"This study will help us better analyse and focus our efforts to fight movie theft," said MPAA's Dan Glickman.
Bootlegging, which the study defines as buying illegally copied films, DVDs or video CDs, was said to account for $2.4 billion in lost revenue. Illegal copying - which included viewers making copies for their own personal use - made up $1.4 billion of the estimated yearly loss.
In the United States, illegal copying is the most prominent way to get pirated movies, whereas in other countries, downloads and bootlegging are more commonly used.
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