Hollywood laid much of the blame for illegal movie downloading on college students. Now, it says its math was wrong.

In a 2005 study it commissioned, the Motion Picture Association of America claimed that 44 per cent of the industry's domestic losses came from illegal downloading of movies by college students, who often have access to high-bandwidth networks on campus.

The MPAA has used the study to pressure colleges to take tougher steps to prevent illegal file-sharing and to back legislation currently before the House of Representatives that would force them to do so.

But now the MPAA, which represents the U.S. motion picture industry, has told education groups a "human error" in that survey caused it to get the numbers wrong. It now blames college students for about 15 per cent of revenue loss.

The MPAA says that's still significant, and justifies a major effort by colleges and universities to crack down on illegal file-sharing. But Mark Luker, vice-president of campus IT group Educause, says it doesn't account for the fact that more than 80 per cent of college students live off campus and aren't necessarily using college networks.

He says three per cent is a more reasonable estimate for the percentage of revenue that might be at stake on campus networks.

"The 44 per cent figure was used to show that if college campuses could somehow solve this problem on this campus, then it would make a tremendous difference in the business of the motion picture industry," Luker said. The new figures prove "any solution on campus will have only a small impact on the industry itself," he said.

The original report, by research firm LEK, claims the U.S. motion picture industry lost $6.1 billion US to piracy worldwide, with most of the losses overseas. It identified the typical movie pirate as a male aged 16 to 24. MPAA said in a statement that no errors had been found in the study besides the percentage of revenue losses that could be attributed to college students, but that it would hire a third party to validate the numbers.

"We take this error very seriously and have taken strong and immediate action to both investigate the root cause of this problem as well as substantiate the accuracy of the latest report," the group said in a statement.

Terry Hartle, vice-president of the American Council on Education, which represents higher education in Washington, said the mistakes showed the entertainment industry has unfairly targeted college campuses.

"Illegal peer-to-peer file-sharing is a society-wide problem. Some of it occurs at colleges and universities but it is a small portion of the total," he said, adding colleges will continue to take the problem seriously, but more regulation isn't necessary.