Torrentfreak is not a reliable news source by any means. It has a strong agenda and that article spun the findings of the paper.

"Our findings indicate that, as a lower bound, international box office returns in our sample were at least 7% lower than they would have been in the absence of pre-release piracy. By contrast, we do not see evidence of elevated sales displacement in US box office revenue following the adoption of BitTorrent, and we suggest that delayed legal availability of the content abroad may drive the losses to piracy." (Italics are mine)

Here's a link to the actual paper: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1986299

Did you read the paper though?

"Taking this triple-difference [their metric for determining piracy rate] as a conservative estimate of the effect of piracy on box office sales, we infer that pre-release piracy causes the foreign box office returns for a movie to decrease by 1.3% for each week of lag between the U.S. release and the foreign release of the movie."

...

"We estimate that movies in our data would have returned a total of nearly $3.52 billion if not for piracy, implying that piracy caused films to lose $240 million in weekend box office returns in the non-US countries in our data during 2005. Thus we estimate that weekend box office returns in our data were about 7% lower than they would have been in the absence of pre-release piracy. This estimate may be conservative if the actual losses to piracy are greater than those suggested by our tripledifference estimate or if returns in the US box office are also reduced by piracy."

Also, the paper only talks about box-office sales, not even touching the DVD/Blu-ray/download market.