The influence of journal self‐citations on journal impact factor and immediacy index

The purpose of this research is to investigate the relationship between journal self‐citation and journal impact factor (JIF)/journal immediacy index (JII).

This research examined research papers in 20 key journals in environmental engineering with a publication year range of 1999 to 2008. The bibliographical information of cited references was obtained from the Science Citation Index Expanded of the Web of Science.

The findings indicated that JIF and JII values changed only slightly regardless of the inclusion or exclusion of self‐citations, suggesting that the influence of self‐citation on journals was insignificant. Consequently there is no need for evaluations to exclude journal self‐citations in journal or researcher evaluations. In addition the findings indicated that JIF and five‐year JIF were highly correlated, suggesting that it would not be necessary to extend the calculation of JIF to five years. Considering the cost in terms of time and effort, the two‐year JIF is sufficient in the discipline of environmental engineering.

This research provides a better understanding of journal self‐citations in journal or researcher evaluation with JIF and JII as indicators.