The journal Impact Factor (IF) is not comparable among fields of Science and
Social Science because of systematic differences in publication and citation
behaviour across disciplines. In this work, a decomposing of the field
aggregate impact factor into five normally distributed variables is presented.
Considering these factors, a Principal Component Analysis is employed to find
the sources of the variance in the JCR subject categories of Science and Social
Science. Although publication and citation behaviour differs largely across
disciplines, principal components explain more than 78% of the total variance
and the average number of references per paper is not the primary factor
explaining the variance in impact factors across categories. The Categories
Normalized Impact Factor (CNIF) based on the JCR subject category list is
proposed and compared with the IF. This normalization is achieved by
considering all the indexing categories of each journal. An empirical
application, with one hundred journals in two or more subject categories of
economics and business, shows that the gap between rankings is reduced around
32% in the journals analyzed. This gap is obtained as the maximum distance
among the ranking percentiles from all categories where each journal is
included.Comment: 28 pages, 4 tables and 5 figures. arXiv admin note: text overlap with
arXiv:1007.4749 by other author
