Quantifying Global Transfers of Copyrighted Content Using BitTorrent
41 Pages Posted: 16 Jan 2012 Last revised: 18 Jan 2012
Date Written: September 24, 2011
This paper presents the most accurate empirical study to date to characterize and quantify the amount of content of various types that is transferred worldwide using BitTorrent, the dominant peer-to-peer (P2P) file sharing application. Using data we collected from the largest public BitTorrent tracker over 106 days between August 2010 and February 2011 and a new methodology, we find that for some content types, the number of copies transferred is an order of magnitude greater than the number sold through legal channels. For example, we estimate that 10.7 songs were transferred using BitTorrent for every song sold, 3.6 movies were transferred using BitTorrent for every legal sale or rental of a DVD or Blu-ray, and 227 movies were transferred using BitTorrent for every paid download. We also find that the vast majority of music and video content transferred using BitTorrent is copyrighted, as demonstrated both by the swarm metadata we observed, and the fact that only 0.55% of the transfers were of files indexed by websites that specialize in content that can be transferred legally.
Thus, we conclude that BitTorrent transfers result in hundreds of millions of copyright violations worldwide per day, and that copyright holders fail to realize significant revenues as a result. Movies are the type of content most supplied and most transferred in BitTorrent (shared in 38.7% of swarms and accounting for 26.1% of transfers). Songs and software, despite being shared in small percentages of swarms (4.5% and 7.2% of swarms respectively), rank 2nd and 3rd in terms of transfers (with 20.4% and 16.8% of transfers respectively). This shows the limitations of past studies that estimated the economic impact of P2P by looking at which content is available rather than trying to measure the number of actual transfers. Surprisingly, most of the copies transferred using BitTorrent come from a small number of extremely popular titles; 37 song titles account for half of all songs transferred, and 117 movies account half of all movie transfers. Thus, for a global marketplace, the importance of the “long tail” of less popular content is smaller than we and others have observed in more localized studies. In general, the content that is popular in legal channels is also popular with BitTorrent, but we observe some important differences. For example, we find that content that is popular among teenagers is more likely to be disproportionally represented in BitTorrent transfers as compared to content that appeals to an older audience.
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