The value of public domain photographs is worth about a quarter of a billion dollars a year to Wikipedia, according to a new research paper. The authors studied the biographical Wikipedia pages of authors, composers, and lyricists to determine whether the public domain status of available images leads to cost savings and increased visitors to individual pages.

“We find that the large majority of photos and illustrations used on subject pages were obtained from the public domain, and we estimate their value in terms of costs saved to Wikipedia page builders and in terms of increased traffic corresponding to the inclusion of an image,” the paper says. The authors estimate a total value of public domain photographs on Wikipedia of $246 million to $270 million dollars per year.

The paper, The Valuation of Unprotected Works: A Case Study of Public Domain Photographs on Wikipedia, is by Paul J. Heald (University of Illinois College of Law), Kris Erickson, and Martin Kretschmer (both University of Glasgow).