Tuesday, February 21, 2012

Bibliometrics and Book Retention

As I've stated in other contexts, selection and deselection represent the same intellectual activity, performed at different points in a book's lifecycle. Deselection has one significant advantage, though. It can be based on a track record of circulation, in-house use, and appearance on authoritative lists. We began to explore yet another type of historical evidence in a previous post on The Impact of Books: citation counts. Although it seems reasonable to presume that the number of citations to a book would correlate with discovery and use, we need a deeper understanding of the underlying dynamics. Highly-cited books seem likely to be important books, books worth keeping, books more likely to be wanted in future.

Bibliometrics "uses quantitative analysis or statistics to describe patterns of publication within a given field or body of literature." Not surprisingly, bibliometric techniques originated in the hard sciences and in the journal literature, but they are now used in many disciplines and increasingly on monographs. Historically, citation analysis has been used to evaluate researchers and departments, and to gauge the impact of a contribution to its discipline. Our purposes are related but somewhat narrower. We are seeking to identify high-impact books within a discipline to assure that they are retained. Can bibliometrics help identify these titles? What can citation patterns tell us about how intellectual content ages in specific disciplines?

Conceptually, this turns out to be a rich vein. and the literature and data run deep. Consider some of these potential data points:
  • Total number of citations: a straightforward measure of citation frequency. However, it may be useful to distinguish between journal-to-book citations and book-to-book citations. The former can be easily (though partially) retrieved through journal indexes. The latter are beginning to be identified using Google Books and Hathi Trust, but at present are largely unavailable.
  • Average citation frequency: Number of citations per monograph in a discipline. Used to compare activity among disciplines.
  • Citation peak: date after publication at which the maximum number of citations occur.
  • Noncitation ratio or Uncitedness Index: absence of citations in a defined time period.
  • Price's Index (citation recency): "calculates the proportion of the number of citations no more than five years old over the total number of citations an item receives."
  • Half-life of citations: a measure of "obsolescence" of scholarly literature, obtained by "subtracting the publication year of source documents from the median publication year of citing documents."
  • Reference decay: the point after which 90 % of citations to a work occur.
There are obvious implications here for monographs deselection and retention. These measures provide one kind of insight into the impact and staying power of individual works. They also enable identification of content aging patterns at the disciplinary level, especially when examined by the periods of "knowledge diffusion" or "intellectual acceptance" developed by Lindholm-Romantschuk and Warner (in "The Role of Monographs in Scholarly Communication: An Empirical Study of Philosophy, Sociology and Economics"). These periods are:
  • Initial Reception: "the period of three calendar years from publication (including the year of publication).
  • Intellectual Survival: the number of years after initial reception that a book continues to be cited.
In an eye-opening 2008 article entitled "Citation Characteristics and Intellectual Acceptance of Scholarly Monographs" Professor Rong Tang of Simmons College employs a number of these concepts to "explore disciplinary difference in the citing of books." Her work centers on 750 randomly selected monographs, 125 each in Religion, History, Psychology, Economics, Math, and Physics. The study seeks to answer two research questions:
"Are there significant domain or disciplinary differences in the distribution of citations to monographs, half-lives, and Price's Index?"
"If conditioned on the periods of intellectual acceptance, are there significant differences among disciplines in terms of citation frequency and number of books cited per period?"
The article presents its methods, concepts, and results clearly. It is well worth reading in its entirety. The table reproduced below begins to show the potential variability across disciplines:

Rong Tang, "Citation Characteristics and Intellectual Acceptance of Scholarly Monographs"

Some of its more surprising results include:
  • Psychology received the highest number of citations, with more than 6,000 and an average of 48.1 citations per monograph, followed by math and physics. History received an average of 3.2 citations per item.
  • Physics has the longest half-life, while humanities disciplines have the shortest.
  • The highest uncitedness ratios occurred in history (52%) and Religion (59%).
  • "...the peak time of citations for six disciplines all occurred within the first 20 years of publication."
  • "Religion and history reached their highest citation amount within the first five years...whereas psychology, physics and mathematics did not receive their citation heyday until more than six years after publication."
  • Citations of most disciplines increase at six years after publication. "The highest potential period of intellectual acceptance is the first 10 years, with the decline and gradual ending of citations during the 11th to 30th years...
It will take time and experimentation to evaluate to determine how applicable some of these ideas and findings may be to book retention decisions. The results need to be qualified: the sample size was small; it considers only article-to-book citations, not book-to-book citations, which may under-represent humanities citations. But the article provides an excellent foundation. A hearty thanks to Professor Tang and predecessors for providing this useful framework.

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