Abstract
While the potential for intellectual property rights to inhibit the diffusion of
scientific knowledge is at the heart of several contemporary policy debates,
evidence for the "anti-commons effect" has been anecdotal. A central issue in
this debate is how intellectual property rights over a given piece of knowledge
affect the propensity of future researchers to build upon that knowledge in
their own scientific research activities. This article frames this debate around
the concept of dual knowledge, in which a single discovery may contribute to
both scientific research and useful commercial applications. A key implication
of dual knowledge is that it may be simultaneously instantiated as a scientific
research article and as a patent. Such patent-paper pairs are at the heart of
our empirical strategy. We exploit the fact that patents are granted with a
substantial lag, often many years after the knowledge is initially disclosed
through paper publication. The knowledge associated with a patent-paper pair
therefore diffuses within two distinct intellectual property environments - one
associated with the pre-grant period and another after formal IP rights are
granted. Relative to the expected citation pattern for publications with a given
quality level, anti-commons theory predicts that the citation rate to a
scientific publication should fall after formal IP rights associated with that
publication are granted. Employing a differences-in-differences estimator for
169 patent-paper pairs (and including a control group of other publications from
the same journal for which no patent is granted), we find evidence for a modest
anti-commons effect (the citation rate after the patent grant declines by
between 9 and 17%). This decline becomes more pronounced with the number of
years elapsed since the date of the patent grant, and is particularly salient
for articles authored by researchers with public sector affiliations.