MOTTO:

                "There is something still worse, however, than being either criticised or dismanteled

                by careless readers: it is being ignored. Since the status of a claim depends on later

                users� insertions, what if there are no later users whatsoever? This is the point that

                people who never come close to the fabrication of science have the greatest difficulty

                in grasping. They imagine that all scientific articles are equal and arrayed in lines

                like soldiers, to be carefully inspected one by one. However, most papers are never

                read at all. No matter what a paper did to the former literature, if no one else does

                anything with it, then it is as if it never existed at all. (Latour, 1987, p. 40)".
 
 

Bibliometric indicators currently used to examine and evaluate the published knowledge production are primarily based on impact factors of journals covered by Science Citation Index database and published annually since 1975 in the Journal Citation Reports [Garfield (Editor)]. This concept has been introduced by Garfield [Garfield, 1972, 1979] as a measure of the average citation frequency for a specific citable item (article, review, letter, discovery account, note, abstract) in a specific journal during a specific year or period. Commonly, the impact factor of a journal is defined as the ratio between citations and recent (previous two years) citable items published, or, in other words, as the average number of citations in a given year of articles published in that journal in the preceding two years. Thus, for instance, the impact factor for 1990 of Physical Review Letters (PRL) has been calculated as the cumulated number of 22,007 citations received in 1990 for articles published in the considered journal in 1988 (11,497 citations) and 1989 (10,510 citations), divided by the cumulated number 2901 (in 1988 + 1989) = 1430 (in 1988) + 1471 (in 1989) of citable articles published in that journal during the same two-year period; the impact factor of PRL in the year 1990 results then from the ratio 22,007 citations / 2901 papers = 7.586 citations per paper and has the meaning of number of citations received by the "average PRL article" during the considered two-year period. Obviously, the definition can be extended over longer time spans. For more detailed recent information about impact factors and their applications, see also ISI Essays [Garfield, 1994; Katz].

Developed originally from the need to compare the journal influence or performance, the impact factor provides nowadays the main quantitative tool for ranking, evaluating, categorising, and comparing journals. Thus, it provides librarians a tool for the management of journal collections and publishers a quantitative evidence in evaluating the position of their journals. But data can as well be ranked to reveal interesting facts about individual or collective performance and trends, such as highly cited papers and authors (hot papers, hot scientists), most active laboratories, institutions or research fronts [Garfield, 1994], up to countries and world science mapping and policy [Garfield, 1994; Katz; Braun].

"Perhaps the most important and recent use of impact is in the process of academic evaluation. The impact factor can be used to provide gross approximation of the prestige of journals in which individuals have been published. This is best done in conjunction with other considerations such as peer review... Again, the impact factor should be used with informed peer review" [Garfield, 1994]. Methods and techniques are currently designed for evaluation and comparison of research groups and individual scientists, such as the so called ISI�s Expected Citation Rates (ECR) System [Garfield, 1994]. A simple scientometric evaluation criterion of individual contributions in fundamental science has recently been proposed [Popescu, 1994] and successfuly tested for promotion thresholds in physics research institutes and faculties [MNE, 1999]. Thus, a particularly direct and transparent cumulative scientometric indicator appears to be the sum of the (journal impact factor, q_i) / (article author number, a_i) ratio or, shortly, S (q_i/a_i), extended over the whole list (assumed statistically significant) of scientific publications of the assessed individual. Obviously, this individual cumulative factor has the meaning of author�s total number of citations per author in the first two years after publication and, consequently, its unit is cites/author at this paper age. Similarly, the average journal impact factor pertaining to an author, S (q_i/a_i)/S (1/a_i), is a measure of his number of citations per published paper, with the corresponding cites/paper unit.

Clearly, a high number of citations means a major impact in the specific field or a high utility. However, it is critical to take into account, among other aspects, that publication and citation rates, as well as the peak impacts, vary widely from field to field, and among different disciplines, and we need to know what the average citation rate is within a field and a discipline to assess an individual. A convenient way to consider this requirement consists in the use of the relative ranking number, r_i , of the journal within its discipline instead of the impact factor, q_i , as far as, according to the Lavalette ranking law [Lavalette, 1996; Popescu, 1997], there exists a simple functional dependence between them, namely q_i = a [(N+1)/r_i - N]-b , where a and b are two fitting parameters, N is the total number of journals in the considered discipline, and r_i = (N- n_i+1)/N is the relative ranking number, corresponding to its (descending) ranking number n_i . Thus, for instance, a value r_i = 0.75 means that 75 % of journals of the considered discipline have a relative ranking number (and the corresponding impact factor) lower or equal to that of the considered journal. Our recommendation for interdisciplinary comparisons and evaluations consists in the use of the individual cumulative relative rank S (r_i/a_i), with its natural unit relative rank, rather than S (q_i/a_i) cites/author. The major advantages of this replacement consist in (i) a bibliometric equivalence of journals belonging to various disciplines but having the same relative ranking number, besides (ii) a much higher stability as compared to the corresponding impact factor.

In order to meet the increasing needs of journal impact factors for a variety of purposes, this work presents a completed and updated version of the previous one (Popescu, version December 1999) and consists in a selection from SCI Journal Citation Reports of almost 6000 journals of general and special interest to scientists engaged in physics, mathematics, chemistry, and related engineering and life sciences. This version covers all available journal impact factors along 24 years in the window 1974-1998, except the missing (not edited) 1976 year. Thus, below are given the tables containig average impact factors (rounded to two decimals) of 6 fields (Table 1), 55 disciplines (Table 2), and 5762 journals (Table 3). For convenience, Table 3 shows the discipline and journal rank (JRK) at the left of the journal title column, and the average journal impact factor (JIF), standard deviation (DEV) and the number of years of ISI quotation (YRS) at right. Generally, the journal relative ranking r_i = (N- n_i+1)/N ranges from unity (for top journals) to 1/N (for bottom journals), so that various discipline and field average relative rankings are close to 1/2. Also, the overall science average impact factor is about unity. Thus, according to Table 1, the average field rank (FRK) is 0.55 whereas the average field impact factor (FIF) is 1.11. Due to this circumstance, the promotion, appointment, and accreditation thresholds in the ranking S (r_i/a_i) scale should be roughly half of those established in the cites S (q_i/a_i) scale. Also, in the available 24 years window of ISI quotation, the average journal lifetime amounts close to one half thereof (12.1 years). A further edition of the present work will contain in addition the complete annual distribution of journal impact factors showing the "ever-changing river of journals". Though far from perfect, the new indicators proposed here allow to examine several key facets of an important part of individual and collective knowledge production.
 
 

Prof. dr. Ioan-Iovitz Popescu

Member of the Romanian Academy

Bucharest

July 2000
 
 

REFERENCES
 

TABLE 1: FIELD IMPACT FACTORS
 

TABLE 2: DISCIPLINE IMPACT FACTORS
 

TABLE 3: JOURNAL RANKS AND IMPACT FACTORS
 
 
 
 
 
 

REFERENCES
 
 

Braun T. (Editor-in-Chief), Scientometrics, An International Journal for all Quantitative Aspects of the Science of Science, Communication in Science and Science Policy, Elsevier, P.O.Box 330, 1000 AH Amsterdam, The Netherlands; Akadémiai Kiadó, P.O.Box 245, H-1519 Budapest, Hungary

Garfield E. (Editor), Science Citation Index, Journal Citation Reports: a bibliometric analysis of science journals in the ISI database, Institute for Scientific Information, Philadelphia, PA, USA. The URL of the Institute for Scientific Information (ISI) Web site is http://www.isinet.com

Garfield E., Citation Analysis as a Tool in Journal Evaluation, Science, 178, 471- 479 (1972); Citation Indexing, Its Theory and Application in Science, Technology, and Humanities, John Wiley & Sons, New-York (1979); The Impact Factor, Current Contents, 25, 3-7 (June 20, 1994); Using the Impact Factor, Current Contents, 29, 3-5 (July 18, 1994); Expected Citation Rates, Half-Life, and Impact Ratios, Current Contents (September 12, 1994); Research Fronts, Current Contents, 41, 3-7 (October 10, 1994); Scientography: Mapping the Tracks of Science, Current Contents (November 7, 1994); available also at http://www.isinet.com/hot/essays

Katz J. S., Questions of Collaboration (with Hicks D. M.), Nature, 375, 99 (11 May 1995); Desktop Scientometrics, Scientometrics, 8 (1) 141-153 (1997); What is Research Collaboration (with Martin B. R.), Research Policy, 26, 1-18 (1997); Indicators for Systems of Innovation: A Report on the IDEA (Indicators and Data for European Analysis) Project (with Hicks D. M.), IDEA Paper Series, 12, 1-66 (1998); The Self-Similar Science System, Research Policy, 28, 501-517 (1999); Scale-Independent Indicators and Research Evaluation, Science and Public Policy (6 March 2000); some available at http://www.sussex.ac.uk/spru/jskatz; http://www.sol.no/step/IDEA

Latour B., Science in Action, Milton Keynes: Open University Press (1987)

Lavalette D., Facteur d�impact: impartialité ou impuissance ?, Internal Report, INSERM U350, Institut Curie - Recherche, Bât. 112, Centre Universitaire, 91405 Orsay, France (November 1996)

MNE (Romanian Ministry of National Education), Order No. 5103 dated on 05.07.1999, Annex 1-II

Popescu I.-Iovitz, A Simple Scientometric Assessment of Individual Contributions in Fundamental Physics, Romanian Reports in Physics, 46, 899-905 (December 1994); On the Lavalette Ranking Law (with M. Ganciu, M. C. Penache, and D. Penache), Romanian Reports in Physics, 49, 3-27 (January 1997); Journal Impact Factors of Interest to Basic Sciences, Version December 1999, Editura Horia Hulubei (December 1999); Journal Ranking and Average Impact Factors of Basic and Allied Sciences, Version July 2000, Editura Horia Hulubei (October 2000).
 
 

TABLE 1: FIELD IMPACT FACTORS
 
 

Field Journal Number (N)

Average Field Impact Factor (FIF)

Average Field Rank (FRK)
 

FIELD	N	FIF	FRK
BIO	2469	1.43	0.54
CHEM	551	1.34	0.55
ENG	1210	0.57	0.55
MATH	671	0.46	0.55
PHYS	687	1.28	0.56
SCI	175	0.87	0.56
	SUM = 5762	AVERAGE = 1.11	AVERAGE = 0.55

 
 
 

TABLE 2: DISCIPLINE IMPACT FACTORS

Discipline Journal Number (N)

Average Discipline Impact Factor (DIF)

Average Top Journal Impact Factor (TJIF)
 

ID	DISCIPLINE	N	DIF	TOP JOURNAL TITLE	TJIF
1	BIO-BIOCHEM	299	2.59	Annu Rev Biochem	34.70
2	BIO-BIOL	336	1.65	Cell	24.08
3	BIO-BIOPHYS	49	2.06	Annu Rev Biophys	8.59
4	BIO-BIOTECH	63	1,20	Nat Biotechnol	7.74
5	BIO-BOT	219	0.79	Annu Rev Plant Phys	13.48
6	BIO-ENVIRON	178	0.91	Annu Rev Ecol Syst	4.15
7	BIO-FOOD	120	0.49	Crit Rev Food Sci	1.54
8	BIO-GENET	109	2.34	Nat Genet	30.27
9	BIO-IMMUN	166	2.51	Annu Rev Immunol	32.59
10	BIO-MED	207	1.32	Clin Res	50.57
11	BIO-MICRO	141	1.68	Microbiol Rev	16.83
12	BIO-PHARM	254	1.38	Pharmacol Rev	17.99
13	BIO-RAD	75	1.01	J Nucl Med	3.66
14	BIO-ZOOL	253	0.56	Annu Rev Entomol	4.25
15	CHEM	136	1.31	Chem Rev	11.46
16	CHEM-ANAL	61	1.31	Anal Chem	3.67
17	CHEM-APPL	79	0.78	Angew Chem	5.30
18	CHEM-INORG	30	1.64	Prog Inorg Chem	8.90
19	CHEM-ORG	44	1.70	Adv Organomet Chem	8.12
20	CHEM-PHYS	112	1.81	Surf Sci Rep	10.40
21	CHEM-POLYM	89	0.90	Adv Polym Sci	3.45
22	ENG-CHEM	97	0.39	AICHE J	1.16
23	ENG-COMPUT	121	0.51	Commun ACM	1.61
24	ENG-ELECTR	140	0.35	P IEEE	2.20
25	ENG-ENERG	50	0.36	Prog Energ Combust	1.34
26	ENG-GEO	297	0.87	J Geophys Res	4.03
27	ENG-IMAG	58	0.66	Vision Res	1.76
28	ENG-INSTR	62	0.54	Biol Mass Spectrom	2.13
29	ENG-MATER	127	0.68	Prog Mater Sci	4.48
30	ENG-MECH	61	0.25	J Microelectromech	1.29
31	ENG-METALL	94	0.35	Acta Metall	1.94
32	ENG-NUCL	54	0.56	Radiat Res	1.97
33	ENG-SPACE	48	0.31	Space Sci Rev	1.87
34	MATH	150	0.39	Ann Math	1.62
35	MATH-APPL	106	0.53	Siam Rev	1.33
36	MATH-CYB	104	0.61	Artif Intell	2.50
37	MATH-INFO	128	0.50	IEEE T Inform Theory	1.30
38	MATH-MANAG	123	0.29	Siam J Optimiz	1.40
39	MATH-STAT	60	0.64	Econometrica	1.91
40	PHYS	120	1.58	Rev Mod Phys	16.76
41	PHYS-ACOUST	33	0.66	Hearing Res	1.74
42	PHYS-APPL	63	0.92	Appl Phys Lett	3.37
43	PHYS-ASTRO	46	1.81	Annu Rev Astron Astr	9.66
44	PHYS-ATOM	61	1.99	Prog Nucl Mag Res Sp	6.41
45	PHYS-COND	56	1.54	Solid State Phys	13.22
46	PHYS-CRYST	28	0.98	Acta Crystallogr D	3.08
47	PHYS-FLUIDS	50	0.71	Annu Rev Fluid Mech	3.70
48	PHYS-MATH	22	1.15	Commun Math Phys	2.18
49	PHYS-MECH	46	0.50	Adv Appl Mech	2.16
50	PHYS-METEO	37	1.17	J Climate	3.01
51	PHYS-NUCL	26	2.15	Adv Nucl Phys	8.33
52	PHYS-OPTICS	81	0.89	Prog Optics	3.20
53	PHYS-PLASMA	18	1.13	Nucl Fusion	2.41
54	SCI-EDUC	42	0.33	J Med Ethics	0.72
55	SCI-GEN	133	1.05	Nature	16.10
	SUM N / AVERAGE	5762	1.11

TABLE 3: JOURNAL RANKS AND IMPACT FACTORS
 
 

JIF = Average Journal Impact Factor

DEV = Standard Deviation

YRS = Number of Years of ISI Quotation

NOTE 1: For YRS = 1 one denotes DEV = 0

NOTE 2: + (plus sign) following some abbreviated journal titles indicates combined original (mostly Russian) and English translation