The Thomson Reuters for impact factor report for a given year, sometimes recompiled by various entities into PDF format, typically includes the impact factor for over 7,000 journals and may also include each journal's ISSN and abbreviated title, total citations, number of articles the assigned impact factor is based on, the country where the journal is published or the journals rank relative to other journals. The impact factor is a widely-used measure of a journal's quality.
The impact factor is a metric compiled annually by Thomson Reuters, disseminated via their Journal Citation Report, designed to measure a journal's quality and influence based on the number of times articles in the journal are cited and other factors. Impact factors are widely used as a metric around the world. Many librarians use impact factor data to decide which journals to include in a library's holdings while many authors use impact factor rankings to decide where to submit articles for publication.
Stephen Curry, a writer and Professor of Structural Biology at Imperial College, London has criticized the metric because it often skews a ranking in favor of a journal based on a large number of citations of relatively few articles published in the journal. Other metrics have been used instead of the impact factor, such as the Eigenfactor, immediacy index, cited half-life and source-normalized impact per paper score, but the impact factor is the most common metric used today.