Impact Factors: how to get one, how to improve it, how to understand it. Elaine Stott (Journal Publishing Director, Blackwell Publishing) ISAJE Annual Meeting 2 nd September 2006

2 Impact Factor Eugene Garfield created The Science Citation Index (SCI) in 1961 as a quarterly printed index, journals. Aim to look at relationships between researchers – who was citing who? Journal Impact Factor was used for journal selection. Never intended to be used as it is today – librarians, grants, RAE in UK, authors

3 The Impact Factor Citations Time after publication (Years) The average number of citations the average article receives per annum in the 2 years after publication Article published in Jan 2003 will have longer to contribute cites to 2005 IF than an article published in Dec 2004 e.g. the 2005 impact factor will be the total citations in 2005 to articles published in 2003 and 2004 / no. articles published in 2003 and 2004

4 Document Type Letters: Rapidly climbs to citation peak, large proportion of cites in 2 year window – but low absolute number Full Papers: Later citation peak, smaller proportion in 2 year window, but greater longevity Reviews: Latest citation peak of three document types, and greatest longevity. Proportion of cites within impact window is low - but high absolute number of cites

5 Variation in Impact Factors (Mabe & Amin, 2000) Significant variation in mean impact according to subject area Top journal in one field may have a lower impact than bottom journal in another field. Significant effect of multiple authorship Can be field specific. Comparisons should only be made within the same subject areas

6 Impact Factor Fluctuation: Size of Journal Correlation between impact factor fluctuation and size of journal A journal of 200 papers per year might expect up to ± 15 % fluctuation For an impact of 1.5 this would mean a range of implies no significant change

7 Citations Time after publication (Years) The Immediacy Index No. of citations in the current year / No. articles published in that year A measure of skewness of the citation curve i.e. how quickly are the articles being cited? Some evidence that the II appears to be correlated with IF, i.e. a change in II is followed by a change in IF – useful early warning signal.

8 Citations Time after publication (Years) The Cited Half-Life The number of years that the total citations (i.e. citations to articles from all years, rather than only the previous two years) takes to decline to 50% of its value A measure of rate of decline of the citation curve i.e. article longevity 50% of citations No evidence that the cited half-life is correlated with IF

9 Getting an Impact Factor Today covers 8,500 of a total of 20-30,000 journals (c. 35% of all journals). ISI aim to include most internationally influential journals in each subject area 2,000 journals evaluated every year -both new +already included jnls new added each year

10 Getting an Impact Factor ISI aim to include most internationally influential journals in each subject area 2,000 journals evaluated every year -both new +already included jnls new added each year Details on ISI website:

11 Selection criteria for inclusion in ISI database Basic Journal Publishing Standards a. Timeliness of Publication? b. International Editorial Conventions? c. English Language Bibliographic Information? d. Peer Review? Editorial coverage – does the journal add anything new, how does it compare to other journals waiting to be added? International diversity ( take International + best national Journals)? Number of citations

12 Analysis of citations Related journals Top cited institutions Top cited authors Where are top cited papers being published Which subjects are getting most citations

13 Addiction journals Addiction journals are listed in Journal Citation Reports: Science Substance abuse – ( 8 journals) IF range Psychiatry (84 Journals) IF range Pharmacology and Pharmacy (193 Journals) IF range Toxicology (75 Journals) IF range Psychology (60 Journals) IF range Social Science Substance abuse – (18 Journals) IF range Psychology, general – (111 Journal) IF range Psychology, clinical (53 Journals) IF range Social Issues (31 Journals) IF range

Impact factors – Science -substance abuse 1ADDICTION DRUG ALCOHOL DEPEN ALCOHOL CLIN EXP RES ALCOHOL ALCOHOLISM2.04 5ADDICT BIOL ALCOHOL J STUD ALCOHOL SUBST USE MISUSE0.983

Impact factors – Social Science - substance abuse 1 ADDICTION PSYCHOL ADDICT BEHAV J SUBST ABUSE TREAT EUR ADDICT RES J STUD ALCOHOL DRUG ALCOHOL REV ADDICT BEHAV AM J ADDICTION ALCOHOL RES HEALTH AM J DRUG ALCOHOL AB SUBST USE MISUSE J ADDICT DIS J DRUG ISSUES J PSYCHOACTIVE DRUGS J DRUG EDUC DRUG-EDUC PREV POLIC ADDICT RES THEORY J CHILD ADOLES SUBST 0.579

16 Analysis of citations Related journals Top cited institutions Top cited authors Where are top cited papers being published Which subjects are getting most citations

17 Papers in impact factor journals Finland Total articles 98 Total citations 256 Addiction3063 Alcohol & Alcoholism2978 ACER1965 Substance Use & Misuse71 DAD427 Alcohol311 Addiction Biol34 J. Sub. Abuse37