An Assessment of Research-Doctorate Programs in the United States Mathematical and Physical Sciences (1982) / Chapter Skim
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Appendix F: Data on Publication Records (Measures 15 and 16)
Appendix F: Data on Publication Records (Measures 15 and 16)
Pages 220-237
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From page 220... ...
The following pages have been excerpted from Chapters VI and VII of this report and describe operational considerations in compiling the publication records included here (measure 15) and the methodology used in determining the "influence" of published articles (measure 16)
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Later sections of the chapter consider publication and citation count parameters in further detail, including discussions of data bases, of field-dependent characteristics of the literature, and of some cautions and hazards in performing citation analyses for individual scientists. The basic stages which must be kept in mind when doing a publication or citation analysis are briefly summarized in Figure 6-1.
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Furthermore, the timeliness of the secondary sources varies with sources dependent on outride Her lagging lags may ey are a widely, ~ months or even years behind. Since these abstracting depend upon language, field and country of origin, th particular problem in international publication count The Science Citation Index is one of the most current secondary sources, with some80% to 90% of a given year's publications in the SCI for that year.
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This number of publications is far in excess of the normal publication rate of one to two articles per year per scientist. Multiple authorship problems arise less often in institutional publication counts since there are seldom more than one or two institutions involved in one publication.
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Since multiple years of the Citation Index are often involved the amount of clerical work searching from volume to volume and from author to author, and citation to citation can be quite large. A note of caution about the handling of multiple authorship in the Corporate Index of the Science Citation Index: SCI lists a publication giving all the corporate affiliations, but always with the first author's name.
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In a Computer Horizons study completed in 1973 the amount of agency support acknowledgement was tabulated in twenty major journals from five different fields.4 Table 6-1 summarizes those support acknowledgements for 1969 and 1972. In 1969, only 67% of the articles in 20 major journals acknowledged financial support.
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227 or ~4 0 aC to cr' or U' o ~o At: .- o, ~me a ~ ret Z H Cal ' 0 a, 0= .
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Almost 70% of the art responded to the d, over two-thirds t of their regular s cited specific , even though they tself. Twelve perinstitutional supof graduate studies was in Overall, the 1972 tabulation and survey showea that 88% of the research reported in these prestigious journals was externally supported, and that 97% of the externally supported work was acknowledged as such.
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Some of the characteristics of the literature which are revealed by citation analysis are noted on Figure 6-1. These characteristics~include: The dispersion of references: a measure of scientific "hardness", since in fields that are structured and have a central core of accepted knowledge, literature references tend to be quite concentrated.
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The total number of citations to a set of publications, while incorporating a measure of peer group recognition, depends on the size of the set involved and has no meaning on an absolute scale. The journal "impact factor" introduced by Garfield is a size-independent measure, since it is defined as the ratio of the number of citations the journal receives to the number of publications in a specified earlier time period.1 This 1Eugene Garfield, Citation Analysis As a Tool in Journal Evaluation " Science 178 (November 3, 1972)
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The idea of counting a reference from a more prestigious journal more heavily has also been suggested by Kochen.2 A third limitation is that there is no normalization for the different referencing characteristics of different segments of the literature: a citation received by a biochemistry journal, in a field noted for its large numbers of references and short citation times, may be quite different in value from a citation in astronomy, where the overall citation density is much lower and the citation time lag much longer. In this section three related influence measures are developed, each of which measures one aspect of a journal's influence,with explicit recognition of the size factor.
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A citation matrix for a specific time lag may also be formulated. This would link publications in one time period with publications in some specified earlier time period.
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This reasoning provides a first order approximation to the weight of each unit, which is W(1) = total number of citations to the ith unit from other units ~ total number of references from the ith unit to other units This is the starting point for the iterative procedure for the calculation of the influence weights to be described below.
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With the choice of target size Si, the value | = 1 is in fact an eigenvalue so that Equation 1 itself does possess a solution. ACT y Using the notation O for the transpose of ~ r ik ski ; introducing the Rronecker delta symbol (1 i S k defined by J ik to i ~ k _ al the equation can then be written *
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tan . called the characteristic equation.
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Each root of the characteristic equation determines a solution vector or eigenvector of the equation, but the weight vector being sought is the eigenvector corresponding to the largest eigenvalue. This can be seen from the consideration of an alternative procedure for solving the system of equations, a procedure which also leads to the algorithm of choice.
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= ~(km ~ m ~ j=1 m ^ - /ji This provides the most convenient numerical procedure for finding the weights, the whole iteration procedure being reduced to successive squarings of the ~ matrix. This procedure is closely related to the standard method for finding the dominant eigenvalue of a matrix.
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