Page 167 - Becoming Metric Wise

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Journal Citation Analysis

PUB J (Z) denotes the number of articles published in journal J in the
year Z. Again one may omit the index J if it is clear about which journal
one is talking, or when it does not matter. JIF 2 is a synchronous impact
factor. The term “synchronous” refers to the fact that all citations used
to calculate it were given (hence received by the journal) in the same
year. Stated otherwise, these citations can be found in reference lists of
articles published in the same year. Besides a 2-year JIF one can define
an n-year synchronous impact factor in an analogous way (Rousseau,
1988a):
n
P
i51 CITðY; Y 2 iÞ
n n
JIF ðYÞ 5 P (6.3)
i51 PUBðY 2 iÞ
We observe that if n 5 2informula (6.3) one obtains the standard
Garfield-Sher impact factor, formula (6.2). Citation data needed to
compute a synchronous impact factor are found in the same row of a
p-c matrix (Ingwersen et al., 2001). In case the journal is included in
the JCR one can find all necessary data by opening the “Cited Journal”
view in the file corresponding with the year Y. Since edition 2007
Thomson Reuters’ JCR also provides 5-year synchronous impact factors
for journals, i.e., taking n 5 5 in formula (6.3).We will returntothis
point.
Besides Clarivate Analytics (formerly Thomson Reuters) other data-
bases also show JIFs (though usually not called as such). SCImago, for
instance, based on data from the Scopus database, shows a Cites/Doc
(2 years) indicator. The Chinese Science Citation Database (CSCD), the
China Scientific and Technical Papers & Citations (CSTPC) and the
China National Knowledge Infrastructure (CNKI) database in China pro-
vide 2-year synchronous impact factors for Chinese scientific journals. In
the calculation of these impact factors only journals available in these
databases are used (hence these JIFs are based on different pools) (see Jin &
Wang, 1999; Jin et al., 2002; Rousseau et al., 2001; Wu et al., 2004).

6.4.2 An Example and a Warning
0
Let us calculate the standard impact factor of journals J and J for the year
Y. Data necessary for this calculation are shown in Table 6.4. Which jour-
nal has the highest impact factor?
JIF JðÞ 5 30 1 30 5 3:0 and JIF ð J Þ 5 60 1 60 5 2:0. Hence journal J has
0
2 10 1 10 2 30 1 30
the highest impact factor. Now we add, to both journals, 25 uncited articles