Moed HF "Statistical relationships between downloads and citations at the level of individual documents within a single journal " JASIST 56(10):1088-1097, August 2005

[Eugene Garfield]

Henk F. Moed : moed at cwts.leidenuniv.nl

Author(s): Moed, HF

Title: Statistical relationships between downloads and citations at the
level of individual documents within a single journal

Source: JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND
TECHNOLOGY, 56 (10): 1088-1097 AUG 2005

Language: English    Document Type: Article

Abstract:
Statistical relationships between downloads from ScienceDirect of documents
in Elsevier's electronic journal Tetrahedron Letters and citations to these
documents recorded in journals processed by the Institute for Scientific
Information/Thomson Scientific for the Science Citation Index (SCI) are
examined. A synchronous approach revealed that downloads and citations show
different patterns of obsolescence of the used materials. The former can be
adequately described by a model consisting of the sum of two negative
exponential functions, representing an ephemeral and a residual factor,
whereas the decline phase of the latter conforms to a simple exponential
function with a decay constant statistically similar to that of the
downloads residual factor. A diachronous approach showed that, as a cohort
of documents grows older, its download distribution becomes more and more
skewed, and more statistically similar to its citation distribution. A
method is proposed to estimate the effect of citations upon downloads using
obsolescence patterns. It was found that during the first 3 months after an
article is cited, its number of downloads increased 25% compared to what
one would expect this number to be if the article had not been cited.
Moreover, more downloads of citing documents led to more downloads of the
cited article through the citation. An analysis of 1,190 papers in the
journal during a time interval of 2 years after publication date revealed
that there is about one citation for every 100 downloads. A Spearman rank
correlation coefficient of 0.22 was found between the number of times an
article was downloaded and its citation rate recorded in the SCI. When
initial down loads-defined as downloads made during the first 3 months
after publication-were discarded, the correlation raised to 0.35. However,
both outcomes measure the joint effect of downloads upon citation and that
of citation upon downloads. Correlating initial downloads to later citation
counts, the correlation coefficient drops to 0.11. Findings suggest that
initial downloads and citations relate to distinct phases in the process of
collecting and processing relevant scientific information that eventually
leads to the publication of a journal article.

Addresses: Leiden Univ, Ctr Sci & Technol Studies, NL-2300 RB Leiden,
Netherlands

Reprint Address: Moed, HF, Leiden Univ, Ctr Sci & Technol Studies, POB
9555, NL-2300 RB Leiden, Netherlands.

E-mail Address: moed at cwts.leidenuniv.nl

Cited References:
BRODY T, 2002, HT 02 13 ACM C HYP.
GARFIELD E, 1979, CITATION INDEXING.
GARVEY WD, 1971, AM PSYCHOL, V26, P349.
HARNAD S, 2003, MANDATED ONLINE RAE.
HICKMAN I, 2000, MINING SOCIAL LIFE E.
HITCHCOCK S, 2002, OPEN CITATION LINKIN.
HITCHCOCK S, 2003, IMPACT OAI BASED SEA.
MOED HF, 1998, J DOC, V54, P387.
PARKER RH, 1982, J AM SOC INFORM SCI, V33, P129.


Times Cited: 0

Publisher: JOHN WILEY & SONS INC
Publisher Address: 111 RIVER ST, HOBOKEN, NJ 07030 USA
ISSN: 1532-2882
ISI Document Delivery No.: 946WK