Open Access News

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Tuesday, July 18, 2006

Visitation spikes and decays

Z. Dezsö and five co-authors, Dynamics of information access on the web, Physical Review E, June 30, 2006. Only the abstract of the published version is free online, but the preprint is OA at arXiv. (Thanks to the PLoS blog.)
While current studies on complex networks focus on systems that change relatively slowly in time, the structure of the most visited regions of the web is altered at the time scale from hours to days. Here we investigate the dynamics of visitation of a major news portal, representing the prototype for such a rapidly evolving network. The nodes of the network can be classified into stable nodes, which form the time-independent skeleton of the portal, and news documents. The visitations of the two node classes are markedly different, the skeleton acquiring visits at a constant rate, while a news document's visitation peaks after a few hours. We find that the visitation pattern of a news document decays as a power law, in contrast with the exponential prediction provided by simple models of site visitation. This is rooted in the inhomogeneous nature of the browsing pattern characterizing individual users: the time interval between consecutive visits by the same user to the site follows a power-law distribution, in contrast to the exponential expected for Poisson processes. We show that the exponent characterizing the individual user's browsing patterns determines the power-law decay in a document's visitation. Finally, our results document the fleeting quality of news and events: while fifteen minutes of fame is still an exaggeration in the online media, we find that access to most news items significantly decays after 36 hours of posting.

Comment. This paper studies visits to news sites, where the decay in user demand is very rapid. I'd like to see someone study the decay rates for peer-reviewed articles in different disciplines. (Publishers undoubtedly have the relevant data but I haven't see a systematic cross-disciplinary collection and comparison.) I suspect that we'd find a wide range, with faster decay rates in the sciences than the humanities. I also suspect that citation curves would track the decay curves, starting after some lag time and declining with a gentler slope. Studying the decay rates would help us predict citations and determine when, strictly by the standard of publisher revenues, embargoes are too short (opening access before the demand has spiked) or needlessly long (blocking access after the demand has spiked). Even with good data on decay rates, however, it would not follow that a funding agency setting a maximum embargo for its OA policy should give top priority to publisher revenue. But good data would help evaluate publisher objections to proposed embargo periods.