Journal topic citation potential and between-field comparisons: The topic normalized impact factor

The journal impact factor 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 source normalization of the journal impact factor is proposed. We use the aggregate impact factor of the citing journals as a measure of the citation potential in the journal topic, and we employ this citation potential in the normalization of the journal impact factor to make it comparable between scientific fields. An empirical application comparing some impact indicators with our topic normalized impact factor in a set of 224 journals from four different fields shows that our normalization, using the citation potential in the journal topic, reduces the betweengroup variance with respect to the within-group variance in a higher proportion than the rest of indicators analysed. The effect of journal self-citations over the normalization process is also studied.