Passive vs. Active voice

1. MEASURES OF READERSHIP, CITATION AND INFLUENCE Impact factor, Eigenfactor, and h-indexBackground and Basics in Academic Researching and Publishing Passive vs. Active voice Carolyn Brown Taller especializado de inglés científico para publicaciones académicas D.F., México 10-28 de junio de 2013

2. Introduction • In 1955, Eugene Garfield published a paper in Science magazine suggesting that the impact of a scientific journal could be measured • This led to the creation of a statistic based on citations • Full history: http://www.garfield.library.upenn.edu/papers/jifchicago2005.pdf

3. Introduction • The real story, though, is that journals were proliferating, and scientists were looking for a way to distinguish among them • Need a proxy measure to capture readership, citation, and influence • The first was Garfield’s “impact factor” • Now it has a competitor, the Eigenfactor

4. Introduction • Almost from their inception, these statistics for journal influence were incorrectly applied to individual authors or papers • Now there are also statistics for readership, citation, and influence of a particular author’s work

5. How I learned to stop worrying and love the impact factor • The impact factor was created by Garfield and Sher in the early 1960s • It is published annual in the Journal Citation Report (Thomson Reuters Science, used to be ISI) • Thomson Reuters owns and operates science literature databases Current Contents, Web of Science, Web of Knowledge, etc. • http://www.isiknowledge.com/JCR

6. … the impact factor • All viable peer-reviewed journals want to be included in Thomson Reuters databases, and are screened and vetted to meet rigorous criteria before being included • Calculation of a journal impact factor • A= total cites to journal in 1992 from Thomson Reuters databases • B= 1992 cites to articles published in 1990 and 1991 (this is a subset of A) • C= number of articles published in 1990 and 1991 • D= B/C = 1992 impact factor

7. … the impact factor • Seems simple, but has caused competitive fervor for a generation • Publishers and editors love to hate the impact factor — why? • Impact factors are low in certain disciplines such as engineering, in which articles are written to be used in the field rather than cited • There is concern that the impact factor can be manipulated by self-citation (citing your own journal as much as possible in your own journal)

8. … the impact factor • Journals that publish more articles (lower rejection rate) are less cited per article and have lower impact factors • The denominator is supposed to include only scientific articles (although non-scientific articles are included in the numerator). Many journals with non-scientific material debate with Thomson Reuters which articles should be deemed scientific.

9. … the impact factor • What constitutes a good impact factor? • High absolute number? • Good ranking among journals in the category? • Alternative impact factor measures from Thomson Reuters: • Five-year impact factor (suitable for journals with a longer citation half-life) • R-coefficient

10. Relatedness coefficient • Because JCR subject categories can be arbitrary, a new way of categorizing was established, based on inter-relatedness — intercitation among journals • Relatedness coefficient or R max • Now published in JCR with regular categories

11. Eigenfactor • The Eigenfactor Score measures the number of times articles from the journal published in the past five years have been cited in the JCR year. • Like the Impact Factor, the Eigenfactor Score is essentially a ratio of number of citations to total number of articles.

12. Eigenfactor • However, unlike the Impact Factor, the Eigenfactor Score: • Counts citations to journals in both the sciences and social sciences. • Eliminates self-citations. Every reference from one article in a journal to another article from the same journal is discounted. • Weights each reference according to a stochastic measure of the amount of time researchers spend reading the journal.

13. Eigenfactor • Eigenfactor has a separate measure called “Article Influence Score” • The Article Influence Score measures the relative importance of the journal on a per-article basis. It is the journal's Eigenfactor Score divided by the fraction of articles published by the journal. That fraction is normalized so that the sum total of articles from all journals is 1. • The mean Article Influence Score is 1.00. A score greater than 1.00 indicates that each article in the journal has above-average influence. A score less than 1.00 indicates that each article in the journal has below-average influence.

14. The correct use of any of these statistics • Impact factor, Eigenfactor, article influence score… • All of these measure the influence of a journal, not any given paper or author • They are used by publishers to know how influential their journal is, set prices, etc. • They are used by libraries to decide which are the essential journals in the discipline

15. The correct use of any of these statistics • Many university tenure and promotion committees, and many funding bodies, use these stats improperly to judge authors or papers (i.e., number of papers published in CJFAS x IF of CJFAS) • Papers should be judged on citations to that paper alone • Authors should be judged on the citations to their papers only

16. h-index • There is a measure to rate an author’s productivity and influence • Invented by Jorge Hirsch in 2005 • A scholar with an index of h has published h papers, each of which has been cited by others at least h times. Thus, the h-index reflects both the number of publications and the number of citations per publication.

17. h-index • The index is designed to improve upon simpler measures such as the total number of citations or publications. The index works properly only for comparing scientists working in the same field; citation conventions differ widely among different fields.

18. h-index • An h-index can be calculated from any citation database, including Web of Science, Scopus, and Google Scholar (so it is not one invariable number) • It changes during the scientist’s career • Other applications: SCImago has a “country” h-index of the publications and citations for all authors in a particular country

19. h-index • There is now a rival to the h-index, called the g-index (Leo Egghe, 2006) • Given a set of articles ranked in decreasing order of the number of citations that they received, the g-index is the (unique) largest number such that the top g articles received (together) at least g2 citations and each received, on average, at least g citations.

20. Pick the stat that suits you! • Publish or Perish software provides a variety of indices for researchers, using Google Scholar as the database, to put the best light on their publications (http://www.harzing.com/pop.htm)

21. Pick the stat that suits you! • Other measures are being invented as well • SCImago (www.scimagojr.com) has a complex journal ranking metric (SJR) based on citations (data from Scopus) • Also provides country-level SJR and h-index data