Open Access Articles Have a Greater Research Impact Than Articles Not Freely Available
Antelman, Kristin. “Do Open-Access Articles Have a Greater Research Impact?” College & Research Libraries 65.5 (Sep. 2004): 372-82.
Objective – To ascertain whether open access articles have a greater research impact than articles not freely available, as measured by citations in the ISI Web of Science database.
Design – Analysis of mean citation rates of a sample population of journal articles across four disciplines.
Setting – Journal literature across the disciplines of philosophy, political science, mathematics, and electrical and electronic engineering.
Subjects – A sample of 2,017 articles across the four disciplines published between 2001 and 2002 (for political science, mathematics, and electrical and electronic engineering) and between 1999 and 2000 (for philosophy).
Methods – A systematic presample of articles for each of the disciplines was taken to calculate the necessary sample sizes. Based on this calculation, articles were sourced from ten leading journals in each discipline. The leading journals in political science, mathematics, and electrical and electronic engineering were defined by ISI’s Journal Citation Reports for 2002. The ten leading philosophy journals were selected using a combination of other methods.
Once the sample population had been identified, each article title and the number of citations to each article (in the ISI Web of Science database) were recorded. Then the article title was searched in Google and if any freely available full text version was found, the article was classified as open access. The mean citation rate for open access and non-open access articles in each discipline was identified, and the percentage difference between the means was calculated.
Main results – The four disciplines represented a range of open access uptake: 17% of articles in philosophy were open access, 29% in political science, 37% in electrical and electronic engineering, and 69% in mathematics. There was a significant difference in the mean citation rates for open access articles and non-open access articles in all four disciplines. The percentage difference in means was 45% in philosophy, 51% in electrical and electronic engineering, 86% in political science, and 91% in mathematics. Mathematics had the highest rate of open access availability of articles, but political science had the greatest difference in mean citation rates, suggesting there are other, discipline-specific factors apart from rate of open access uptake affecting research impact.
Conclusion – The finding that, across these four disciplines, open access articles have a greater research impact than non-open access articles, is only one aspect of the complex changes that are presently taking place in scholarly publishing and communication. However, it is useful information for librarians formulating strategies for building institutional repositories, or exploring open access publishing with patrons or publishers.
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