Coverage
The coverage of a bibliography (or a library or a database) is how complete it is within its defined limits. The opposite is sometimes termed selectivity, but this term is only appropriate if a conscious selection has taken place. (A a selective bibliography being a bibliography for which the best documents have been chosen). 

Bradford's law of scattering (cf., scattering) is claimed to be able to measure the coverage of a bibliography.

By empirical investigations of the coverage of databases may, for example, its coverage of different document types, coverage of sources in different languages or from different countries, coverage of disciplines, subjects, "paradigms" etc.

Hjørland (1987) examined the coverage of "activity theory" in the PsycINFO database. Søgaard Larsen (1993), Alstrup (1996) and Ingwersen & Lynge (2004) examined the representation of Danish research in international databases.

Jacso (1997)  notes that database quality is judged by many criteria, including content, ease of use, accessibility, customer support, documentation and value-to-cost ratio. The principal factor in determining database quality is content. Database content is defined by the scope and coverage of the database and its currency, accuracy, consistency and completeness. The scope of a database is determined by its composition and coverage, including the time period (length), number of journals and other primary sources (width), number of articles included from journals (depth) and geographic and language distribution. The currency of a database is measured by the time lag between publication of the primary source and availability of the corresponding records in the database. Database accuracy is the extent to which the records are free of misspellings. Consistency is the extent to which records within the database follow the same rules with regard to record structure, format and representation. Record completeness is measured by the consistency with which applicable data elements are assigned to all the records in the database.
These criteria can be evaluated qualitatively and/or quantitatively in order to determine the profile of a database, and to ascertain any needed defensive search strategies. Jacsó reviews the major contributions to the literature of the past few years dealing with content evaluation methods, techniques and results and provides a background summary of milestone studies.

Meho & Spurgin (2005) examined the coverage of Library and Information Science (LIS) in different databases. "With a list of 2,625 items published between 1982 and 2002 by 68 faculty members of 18 American Library Association- (ALA-) accredited LIS schools, hundreds of databases were searched. Results show that there are only 10 databases that provide significant coverage of the LIS indexed literature. Results also show that restricting the data sources to one, two, or even three databases leads to inaccurate rankings and erroneous conclusions. Because no database provides comprehensive coverage of the LIS literature, researchers must rely on a wide range of disciplinary and multidisciplinary databases for ranking and other research purposes."

Poulsen (2006) examined the coverage of references in ISI-indexed journal in the ISI database and provided the following figures:

Set     Items   Description
S1      43093   JN=JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
S2       3215   S1 AND PY=2004
S3       3074   S2 AND DT=ARTICLE

S5      14216   JN=BRITISH JOURNAL OF CANCER
S6       1083   S5 AND PY=2004
S7        670   S6 AND DT=ARTICLE
 

S8       4831   JN=JOURNAL OF COMMUNICATION
S9         62   S8 AND PY=2004
S10        33   S9 AND DT=ARTICLE
 

S12       528   JN=ACM TRANSACTIONS ON PROGRAMMING LANGUAGES AND
S13        28   S12 AND PY=2004
S14        27   S13 AND DT=ARTICLE
 

Literature:

Alstrup, E. (1996). Danske historikere i internationale fagbibliografier. En kvantitativ og kvalitativ undersøgelse af dansk historieforsknings repræsentation i internationale fagbibliografier i tidsrummet 1977-1994. Biblioteksarbejde #46, 19-48.
 

Byrne, A. (1983). How to lose a nation literature - Database coverage of Australian research. Database-The Magazine of Database Reference and Review, 6(3), 10-17. 

Hicks, D. (1999). The difficulty of achieving full coverage of international social science literature and the bibliometric consequences. Scientometrics, 44(2), 193-215.

Hjørland, B. (1987). Virksomhedsbegrebet i Psychological Abstracts. Dansk Psykolognyt, #6, 186- 187. ("Correction" from Jørgen Hunsdahl, #8, p. 263).
 

Hjørland, B. (1992). Psykologisk litteraturproduktion i Danmark. Nogle analyser og betragtninger. Psykolognyt,  46(10), 356-360. Click for fulltext: Hjo1992a.PDF

Ingwersen, P. & Lynge, E. (2004). Dækningsgraden i Science Citation Index af dansk sundhedsvidenskabelig forskning 1998. Ugeskrift for Læger, 166(40), 3493-3497.

Jacso, P. (1997). Content evaluation of databases. Annual Review of Information Science and Technology, 32, 231-267.

Jacso, P. (1998). Analyzing the journal coverage of abstracting/indexing databases at variable aggregate and analytic levels. Library & Information Science Research, 20(2), 133-151.

Meho, L. I. & Spurgin, K. M. (2005). Ranking the research productivity of library and information science faculty and schools: An evaluation of data sources and research methods. Journal of the American Society for Information Science and Technology, 56(12), 1314-1331. http://www.slis.indiana.edu/faculty/meho/meho-spurgin.pdf

Poulsen, C. (2006). Kan et citationsindeks bidrage til evaluering af et forskningsmiljø? Dansk Biblioteksforskning, 2(3), 29-39.
 

Søgaard Larsen, M. (1993). Dansk pædagogisk forsknings repræsentation i internationale databaser 1-2. Biblioteksarbejde #38, 14,  71-80 & Biblioteksarbejde #41, 1994, 15, 55-64.
 

Tenopir, C. (1982). Evaluation of Database coverage - A comparison of two methodologies. Online Review, 6(5), 423-441.

van Leeuwen, T. N.; Moed, H. F.; Tijssen, R. J. W.; Visser, M. S. & Van Raan, A.F.J. (2001).
Language biases in the coverage of the Science Citation Index and its consequences for
international comparisons of national research performance. Scientometrics, 51(1), 335-346.

See also: Bias;  Content

Birger Hjørland

Last edited: 15-06-2007

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