Private and Social Costs of Patent Trolls

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Thanks go to Chris Torrero for spotting, via beSpacific, "The Private and Social Costs of Patent Trolls", a research paper by James E. Bessen, Michael J. Meurer and Jennifer Laurissa Ford (September 19, 2011). Boston University School of Law, Law and Economics Research Paper No. 11-45.  According to the abstract:

"In the past, non-practicing entities (NPEs) - firms that license patents without producing goods - have facilitated technology markets and increased rents for small inventors. Is this also true for today’s NPEs? Or are they “patent trolls” who opportunistically litigate over software patents with unpredictable boundaries? Using stock market event studies around patent lawsuit filings, we find that NPE lawsuits are associated with half a trillion dollars of lost wealth to defendants from 1990 through 2010, mostly from technology companies. Moreover, very little of this loss represents a transfer to small inventors. Instead, it implies reduced innovation incentives".

This 33-page paper can be accessed via SSRN here.

The paper appears well-researched and is quite persuasive -- but this blogger is not economically gifted and he wonders how it appears to other economists.  Also, he wonders why all the debate, and apparently all the numbers-based research, seems to be related to the United States. How does the troll model which is used here fare when measured against, for example, European patent litigation patterns? Can anyone help? This blog is happy to host reviews and comments on this paper.