How much are Wikipedia's public domain photos worth?

Every so often this Kat is delighted to hear from his imaginative and mercurial friend Paul J. Heald (Richard W. & Marie L. Corman Research Professor; Fellow & Associated Researcher, CREATe, RCUK Centre for Copyright, University of Glasgow). Paul, for those who don't know his work, is the sort of person who likes to turn regular subjects upside and look at them from all sorts of different angles. This time round, teaming up with the University of Glasgow pair of Martin Kretschmer and Kris Erickson, he has produced a paper, "The Valuation of Unprotected Works: A Case Study of Public Domain Photographs on Wikipedia", which you can enjoy in full via SSRN here. Explains Paul:

"It’s the first attempt (that I know of) to put a monetary value on a portion of the public domain —- the value of public domain images on Wikipedia. As you know, the copyright industry has gotten pretty good at estimating the value of its copyrights. Here is a demonstration of a method to value the absence of copyright. I hope you like it".

According to the abstract of this 30-page paper:

"What is the value of works in the public domain? We study the biographical Wikipedia pages of a large data set of authors, composers, and lyricists to determine whether the public domain status of available images leads to a higher rate of inclusion of illustrated supplementary material and whether such inclusion increases visitorship to individual pages. We attempt to objectively place a value on the body of public domain photographs and illustrations which are used in this global resource. We find that the most historically remote subjects are more likely to have images on their web pages because their biographical life-spans pre-date the existence of in-copyright imagery. 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. Then, extrapolating from the characteristics of a random sample of a further 300 Wikipedia pages, we estimate a total value of public domain photographs on Wikipedia of between $246 to $270 million dollars per year.

This Kat is no economist and, though he generally knows when to nod in agreement or shake his head in disagreement when talking with those whose educational and professional background include mathematics, he must confess that he would find it hard to pass an informed comment on the methodology that led the authors of this paper to reach their $246 to $270 million dollar figure. If any readers have comments to make, or light to shed, on this curious piece, he will be delighted to hear from them.

To get an idea of some of Paul's other writings, you can access his SSRN author page here.
Wikipedia's Public Domain Image Resources page here