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Rev. Saúde Pública vol.45 n.3 São Paulo Jun. 2011 Epub Apr 20, 2011
Índice h de docentes en Salud Colectiva en Brasil
Julio Cesar Rodrigues PereiraI; Bruna BronharaII
de Epidemiologia. Faculdade de Saúde Pública (FSP). Universidade
de São Paulo (USP). São Paulo, SP, Brasil
IIPrograma de Pós-Graduação em Saúde Pública. FSP- USP. São Paulo, SP, Brasil
To estimate reference values and the hierarchy function of professors engaged
in Collective Health in Brazil by analyzing the distribution of the h-index.
METHODS: From the Portal of Coordination for the Improvement of Higher Education Personnel (Portal da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior), 934 authors were identified in 2008, of whom 819 were analyzed. The h-index of each professor was obtained through the Web of Science (WoS) using search algorithms controlling for namesakes and alternative spellings of their names. For each Brazilian region and for the country as a whole, we adjusted an exponential probability density function to provide the population parameters and rate of decline by region. Ranking measures were identified using the complement of the cumulative probability function and the hierarchy function among authors according to the h-index by region.
RESULTS: Among the professors analyzed, 29.8% had no citation record in WoS (h=0). The mean h for the country was 3.1, and the region with greatest mean was the southern region (h=4.7). The median h for the country was 3.1, and the greatest median was for the southern region (3.2). Standardizing populations to one hundred, the first rank in the country was h=16, but stratification by region shows that, within the northeastern, southeastern and southern regions, a greater value is necessary for achieving the first rank. In the southern region, the index needed to achieve the first rank was h=24.
CONCLUSIONS: Most of the Brazilian Collective Health authors, if assessed on the basis of the WoS h-index, did not exceed h=5. Regional differences exist, with the southeastern and northeastern regions being similar and the southern region being outstanding.
Descriptors: Authorship and Co-Authorship in Scientific Publications. Credit system and Researcher Evaluation. Scientific Production. Bibliometric indicators. Public Health. Brazil.
Estimar valores de referencia y función de jerarquía de docentes
en Salud Colectiva de Brasil por medio de análisis de distribución
del índice h.
MÉTODOS: A partir del Portal de la Coordinación de Perfeccionamiento de Personal de Nivel Superior 934 docentes fueron identificados en 2008, de los cuales 819 fueron analizados. El índice h de cada docente fue obtenido en la Web of Science mediante algoritmos de búsqueda con control para homonimias y alternativas de grafía de nombre. Para cada región y para Brasil como un todo se ajustó función de densidad de probabilidad exponencial a los parámetros promedio y tasa de decrecimiento por región. Fueron identificadas medidas de posición y, con el complemento de la función probabilidad acumulada, función de jerarquía entre autores conforme el índice h por región.
RESULTADOS: De los docentes, 29,8% no tenían registro alguno de citación (h=0). El promedio de h para Brasil fue 3,1, con mayor promedio en la región Sur (4,7). La mediana de h para el país fue 2,1, también con mayor mediana en el Sur (3,2). Para una estandarización de población de autores en cien, los primeros colocados para el país deben tener h=16; en la estratificación por región, la primera posición demanda valores más altos en el Noreste, Sureste y Sur, siendo en ésta última h=24.
CONCLUSIONES: Evaluados por los índices h de la Web of Science, la mayoría de los autores en Salud Colectiva no supera h=5. Hay diferencias entre las regiones, con mejor desempeño para el Sur y valores semejantes entre Sureste y Noreste.
Descriptores: Autoría y Coautoría en la Publicación Científica. Sistemas de Créditos y Evaluación de Investigadores. Indicadores de Producción Científica. Indicadores Bibliométricos. Salud Pública.
The h-index has attracted wide interest in the academic community since its introduction by Hirsch in 2005. 6 Its attractiveness arises from the possibility to sort scientists on the basis of a single number. This yields an advantage over other indexes that are based on citations, such as those based on the total number of publications, total number of citations or the number of citations per publication.2 Bibliographic databases such as the Web of Science (Thomson Reuters) and Scopus (Elsevier B.V.) have incorporated this calculation for use in evaluating an author's scientific production. The h-index has become an item on the curriculum vitae (CV) of researchers, as is shown by its adoption by the Lattes Platform of the Conselho Nacional de Desenvolvimento Científico e Tecnológico (National Council for Scientific and Technological Development).
The h-index quantifies the cumulative production of an author6, incorporating information about his/her publication record and evaluation by the corresponding scientific community (the impact of citations).5,12 According to Hirsch's definition6, "A scientist has index h if h of his or her Np papers have at least h citations each and the other (Np - h) papers have h < citations each." Therefore, the index measures the number of articles of an author having at least as many citations as the cardinality of the set of articles, e.g., an author who has ten articles published, of which five have at least five citations, has an h-index of 5.
As a bibliometric indicator, the h-index has attracted the attention of Scientometric academics, who have analyzed the advantages and disadvantages of the index and study new opportunities for scientific production modeling. Since 1995, articles analyzing and modeling the index have accumulated in specialized journals: Scientometrics logs 55 of these articles, 23 of which were published in 2009 [search algorithm on WoS: Publication Name=(scientometrics) AND Topic=(H index)]. Journals from various fields of knowledge have devoted editorials to the h-index, and the first editorial was encountered in 2005; 26 editorials in 22 journals were found in WoS [Topic=(H index) AND Year Published=(2008) Refined by: Document Type=(editorial material)].
Despite this interest, the h-value of a given author lacks meaning and does not help in the judgment of merit; this can only be done by comparison with reference values in each field of knowledge. In fact, to contribute semantic content to values of h, Hirsch's original article describes the h-index of notable authors in his field, which is Physics. In Brazil, at least three initiatives for the identification of h-reference values exist.1,8,10
In 2006, Batista et al1 studied Brazilian scientific publications registered by the WoS from 1970 to 2004 for Physics, Chemistry, Mathematics and Biomedical and Life Sciences and determined the highest values of h found in each area. Batista et al.1 proposed a new indicator, in which the h-index is weighted by the number of co-authors, which attracted wide attention from Scientometric researchers.
Mugnaini et al10 provided reference values to judge the magnitude of a given h-index when comparing authors of Academies of Sciences of the United States and Brazil in the following fields: Biomedical Sciences, Health Sciences, Chemistry, Physics, Biology, Agriculture, Earth Sciences Engineering, Mathematics and Human Science.
Luz et al8 found a high correlation between h and other bibliometric indicators in the graduate programs of five institutions of higher education based on the institutional h-index, irrespective of the field of knowledge. In fact, Van Raan12 found an association not only between different numerical indicators but also with the judgments of peers in research groups in Chemistry.
This study aims to estimate the reference values and hierarchy function of graduate researchers in Collective Health based on an analysis of the distribution parameters of the h-index.
The sample size of the scientific production in Collective Health is inaccurate, and it is not identifiable either by institutional affiliation or by publishing vehicle. We examined the set of all graduate researchers in Collective Health in the country to obtain a sample of authors. The names and affiliations of the graduate programs were accessed through the records of the Coordination for the Improvement of Higher Level Personnel (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) in the public domain on the internet.ª The following options were selected: 1) Registration of students; 2) Book of indicators and 3) Collective Health for the year 2008, resulting in the sampling of all Higher Education Institutions (HEIs) and their programs in Collective Health in Brazil. For each HEI, we selected the Faculty option, resulting in the assembly of a list of all professors in Collective Health with information regarding their institutional affiliation, field and academic title. These data formed the database on faculty in Collective Health in Brazil.
Publications of professors were sorted based on the number of "times cited" obtained from the WoS database. The h-index obtained on the "citation report" page was recorded. For each name, we considered different versions of name spelling identified in the citations of CV Lattes and in the "author index" of WoS. The main difficulties of this phase were the presence of homonyms and different name formats used in bibliographic citations. Homonym cases were solved by considering institutional affiliation, recognizing the group by co-authors, consistency of the investigation field and comparison with the Lattes database. For the different bibliographic citation formats, we included the possible names by using an asterisk at the end of capital letters, aiming for a more sensitive search. For example, if the fictitious name "João Adalberto Gonçalvez Silva" were registered as Silva J, Silva JA or Silva JAG on CV Lattes, the name would be queried in WoS as Silva J*, and the information used for solving homonyms would be included in the filter page of WoS for searching the author's h-index. In the case of different authors having the same name in citations, such publications were excluded, and the h-index was automatically recalculated. Publications were compared with those identified in CV Lattes to ensure the validity of the information obtained.
Search algorithm and validation strategies were tested for each professor from March to November 2008. After query standardization on WoS, we proceeded with the collection of updated data in November 2009.
Figure 1 shows the frequency distribution of h-values based on region and suggests a methodological strategy for analysis. The dotted line describes an exponential decay curve, a Lotka characteristic4 (Lotka's Law7) of the h distribution. The theoretical exponential probability distribution and the Pareto are both able to generalize this type of frequency distribution; we chose the first distribution for the adjustment of events from h=0. The exponential probability density function and cumulative distribution function are described as follows:
f(x) = λe-λx e F(x) = 1 - e -λx.
With the assistance of the SPSS statistical package, we fitted the density functions to the frequency data of each region of Brazil. The quality of fit of each function was described by the complement of the residual variance divided by the total variance (R2 adjusted), and estimates of the decline rate (λ) were assessed based on the 95% confidence interval (95% CI) and the descriptive level obtained using Anova.
To define a hierarchy function of h according to the event, we resorted to the complement of the cumulative distribution percentiles:
rank 1100 = rounding to(100e -λh)
Null h values (zero percentiles) corresponded to the last position of a supposed set of discrete and ordered values of 100 h. Values between the 98.5 and 99.49 percentiles indicated first place (both extreme values were rounded to 99 and 100-99=1), and percentiles beyond 99.49 were rounded to zero and considered hors concours - very rare occurrences of 0.5% or less. This statistically suggests a strange element in the set, albeit in the sense of positively highlighting the high performance. The second place corresponded to the percentile values between 97.5 and 98.49 (rounded to 98) and so on. We obtained different order positions among authors in a given set that would reduce the total number of authors to 100. This strategy seeks to balance the hierarchy of exceptional authors and authors with h = 1, providing a distance between authors and last place, as such a position should be reserved for those who do not have any cited articles.
The h-index of 934 authors dispersed over the region, HEI and program are described in Table 1.
Figures 2 and 3 show that the southeastern (SE) and northeastern (NE) regions have more programs and professors: we found an average of 35 professors per program in the SE and 22 in the NE regions. The southern (S) region, although having a smaller number of programs and professors, showed an average of professors per program (15/program) that was more similar to the NW than to the SE. There is only one program with 21 authors in the central-western (CW) region. In the northern (N) region, there is a master's degree program in Collective Health at the Federal University of Acre (approved by the National Board of Education [CNE], Ministry of Education and Culture [MEC] ordinance 458, DOU 04-11-2008 - Endorsed CES/CNE 28/2008, 04-10-2008), but there is no "book of indicators" that allows the identification of authors.
In Table 2, we recorded the results of the analysis of the h-index distribution by region and for the country as a whole. For all regions, we reached a satisfactory adjustment to the exponential probability density function with parameter λ and with statistical significance. For the function adjustment to the data of each region, repeated records of authors from more than one program were ignored. The first line of Table 2 reports the number of authors' records contributed by each region.
The S and SE regions have the lowest proportion of h-indices equaling zero. However, the SE region has a definite shortcoming, having the greatest rate of decline (28% on average for every unit increase in the value of h). A greater rate of decline indicates a larger drop of probability density from h=0 and, consequently, a reduction of the probability of occurrence of higher values of h. Thus, if h=19 places the author at rank 1 in the SE region, this position would require h=14 in the S region.
After adjusting the exponential probability density function, the regions of greatest similarity are the SE and NE regions: their λ parameters of the density function are similar, with a large overlapping of confidence intervals. As a corollary, their means and medians are similar, as are the hierarchy positions for a given h for these two regions.
The hierarchy function in each region (Table 2) aids in the assessment of the position in a given region and for a particular value of h. For example, for h-index = 10 for a hypothetical author in the SE region, we have the following calculation:
rank1100 H"(100e -0,28.10) = 6.
This means that if there were 100 authors in Collective Health in the SE region, this specific author would be ranked sixth. In this region, h=10 corresponds to the 93.92 percentile, whose complement 6.08 yields 6 when rounded. In the CW region, whose average h-index is 2, h=10 corresponds to the first place tied with the authors with h=9 (in both cases, the rank function yields 1 as the result). In the NE region, this author would be in fifth place, and in the S region, this author would be in eleventh place. Again, there are similarities between the SE and NE regions.
In previous studies,11 more similarities between the NE and S regions were found. These regions registered the highest annual growth rates of publications and citations, less dispersion of research interests (i.e., the highest values of the Shannon E-index), a higher proportion of authors cited and a greater engagement in the fields of Experimental and Clinical Medicine. These apparently paradoxical results may be explained based on changes in WoS in 2007 and 2008 (the years separating both studies) in which, seeking to respond to the competition established by Scopus, WoS more than doubled the number of Brazilian journals indexed, with a consequent sudden increase in production records and citations.b The earlier study covered WoS records until December 2005, at which time it indexed 26 Brazilian journals. In 2007, that number rose to 63, and in 2008, it reached its current value of 103.9 WoS also started to record conference proceedings, which should have also extended the recognition of Brazilian scientific production.
However, the dominance of the NE region among the other regions of Brazil is remarkable. The Ministry of Science and Technology has been developing partnerships with research foundations to promote the decentralization of national scientific production, with increased investments in scholarships for states in the N, NE and CW regions. Since it was created in 2003, the Regional Scientific Development Grant (Bolsa de Desenvolvimento Científico Regional) has aimed at attracting and retaining doctors from deprived areas of the country. In 2007, the Brazilian government implemented the law 11.540/2007, which regulates the National Fund for Scientific and Technological Development. According to this law, at least 40% the total funds allocated to the Ministry of Science and Technology will be applied to programs promoting the qualification and the scientific and technological development of the N and NE regions, including their areas of regional development agency coverage. Initiatives such as this can explain the scientific distinction in Collective Health reached by the NE region.
As a limitation of this study, authors in Collective Health in Brazil may not be perfectly represented in the population studies, because these studies were restricted to graduate programs. Brazilian scientific production has had a significant contribution from Public Health professionals who, being exclusive to the management of the Unified Health System (Sistema Único de Saúde), preserve the interests of this research. Examples of such production include various publications, such as the journals administered by the Ministry of Health, e.g., the Epidemiological Bulletin, Mental Health Bulletin, HR Health Book and others.c However, analysis of the h-index behavior of graduate researchers may have provided reference values for evaluation or comparison purposes of the cumulative scientific production of each region, and this can be used as a reference for judging output.
The value of the h-index from the 'citation report' page underestimates the real value of h of authors whose works are not part of the publication records of WoS. The estimate of h can be refined via a 'cited references search', which will also be limited to citations of published articles that are registered in WoS. Any inaccuracy of this metric does not compromise comparisons of measurements taken under the same assumption. The h-index can also be obtained on BV Scopus and Google Scholar, resulting in different values. It is thus inappropriate to compare values of h from different sources.
The h-index has limitations that are the basis for a critical interpretation of the scientific production of an author. Examples are its dependence on the number of years of scientific activity,6 which hinders comparisons of the h-index of young researchers with that of older researchers, an excessive use of self-citation (which can inflate the value of the h-index)13 and the possibility of underestimating the production of "selective authors", i.e., authors who publish fewer papers but ones that have remarkable international impact and receive many citations.3 Moreover, evaluation of the productivity of scientific researchers cannot be restricted to the use of a single indicator. A single number cannot provide more than a rough approximation of an individual's multifaceted profile, and many other factors should be considered in combination when evaluating a researcher.6 The h-index is a tool to evaluate scientific researchers.
The previous11 and present studies agree in concluding that the NE region has equaled the "Sul maravilha" ("southern wonder"), a phrase coined by Henfil (Henrique de Souza Filho, 1944 - 1988). If he were still alive, maybe his character Grauna would acknowledge a "Nordeste maravilha" ("northeastern wonder"), at least in Collective Health.
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Julio Cesar Rodrigues Pereira
Departamento de Epidemiologia
Faculdade de Saúde Pública da USP
01246-904 São Paulo, SP, Brasil
Research funded by Conselho Nacional de Desenvolvimento Científico e Tecnológico (Process nº 308502/2006-0).
Ministério da Educação. CAPES - Caderno de Avaliação.
Brasília; 2007 [cited 2008 Mar]. Available from: http://conteudoweb.capes.gov.br/conteudoweb/CadernoAvaliacaoServlet?acao=filtraArquivo&ano=2008&codigo_ies=&area=22
b Meneghini R. Inusitado aumento da produção científica. In: Tendências e Debates. Folha Sao Paulo. 12 de maio de 2009, p.3.
c Ministério da Saúde. Periódicos Institucionais. Brasília;[s.d.][citado 2011 mar 21]. Disponível em: http://bvsms.saude.gov.br/php/level.php?lang=pt&component=44&item=79