​Impact Factor (JCR)​

  • Not all journals have impact factors.

    • Citation data only for the records indexed by JCR.

    • Limited number of small-sized journals.

    • Limited number of journals in non-English languages.

    • Very few open access journals.

    • New journals do not have Journal Impact Factors.

  • Journal impact factors may vary between different academic disciplines.​

    • Disciplines that use more references per paper is expected to drive up the Impact Factor of the journal.

    • The same journal may be ranked differently depending on the category being reviewed.

  • ​Impact factor depends on the journal's size.

    • ​​​​​Large and small journals are compared equally *Smaller or more specialized journals will tend to have smaller Impact Factors​.

  • Impact factor depends only on the articles that are cited within two years after publication.

  • Self-citation can distort low journal impact factors.

  • Journals with a large proportion of non-citable items (such as editorials) can have lower journal impact factors. Reviewd articles are cited more often and can change results.