Title changes and impact factor
After a title change, two JCR years must pass before the new title fully replaces the previous title in JCR. In the first year after a journal title change, the new title is listed with an Immediacy Index but no impact factor because the article count for the two preceding years, used in Impact Factor calculations, is zero. The superseded title is listed with a normal two-year Impact Factor. One year later, JCR lists separate impact factors for the new title and for the superseded title, but only the new title will have an Immediacy Index. In this second year, the Impact Factor for a new title may be lower than expected because the article count includes only earlier articles. Similarly, the Impact Factor for the superseded title may be higher than expected because it is based upon only older articles. To calculate a unified Impact Factor, you can total the cites to the two previous years and divide that by the sum of the article counts for the two titles. For a listing of journal title changes, where both the new title and the superseded title appear in JCR, see the Journal Title Changes page, which is accessible from the Journal page, the Journal Search page and the Summary List page.