edited by Birger Hjørland and Claudio Gnoli


Library of Congress Subject Headings (LCSH)

Preliminary editorial placeholder article; to be replaced when an author is found for an improved article

Table of contents:
1. Introduction
2. A brief history and description of LCSH
3. Criticisms of LCSH
4. Conclusion

This article briefly introduces the LCSH, its history and structure. The main emphasis is on the criticisms that have been raised against the system, and which stand in strong contrast to the system's worldwide use as well as its seemingly strong place in educational programs in knowledge organization. The article concludes that the low quality of the system represents a problem for research and education in knowledge organization.

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1. Introduction

The Library of Congress Subject Headings (LCSH) are a subject heading system produced by the Library of Congress (LC) in Washington, DC. It is a kind of controlled vocabulary and as such a → knowledge organization system (KOS). A subject heading system is an alphabetical list of terms used for indexing documents. It is different from a → thesaurus, which is also an alphabetical list of terms used for indexing documents. The main difference is that a subject heading system generally consists of pre-coordinated terms (mainly developed for printed catalogs), while a thesaurus generally consists of terms for post-coordinative searching (mainly developed for electronic databases). In Section 2, more information about LCSH in relation to thesauri is provided.

LCSH is used around the world, as Olson (2000, p. 54) wrote:

[I]n libraries and national bibliographies in much of the English-speaking world (e.g. Australia and the United Kingdom), in heterogeneous environments that are more or less officially English-speaking (e.g. Canada and South Africa), in countries with diverse languages that use English as a common language (e.g. Singapore and Nigeria), in countries that use English for its practical external value (e.g. Iceland), alongside translations of LCSH (e.g. in Turkey and Malaysia), and in translation alone (e.g. the Spanish versions which are widely used in Latin America). LCSH-derived lists of subject headings are used in some countries (e.g. Portugal) and in other types of subject access tools (e.g. indexes published by H. W. Wilson Company).

Because of the huge use of LCSH, and because of its widespread inclusion in courses of → library and information science (LIS), and the many textbooks in which the system is described (including Broughton 2012, Chan 2005, Ganendran 2000, Snow 2021, Stone 2000, and Studwell 1990), the study of its quality is very important.

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2. A brief history and description of LCSH

In this article, just a few points about the history of the LCSH are provided. For further information, see Miksa (1983).

The following points in the development of LCSH can be emphasized:

  • LCSH originated in 1898 when LC adopted the American Library Association's List of Subject Headings for Use in Dictionary Catalogs (American Library Association 1895) as the basis for its own list.
  • The first edition of LC's list was published in parts between 1910 and 1914 as Subject Headings Used in the Dictionary Catalogues of the Library of Congress (Library of Congress 1910–1914).
  • The title of this list became Library of Congress Subject Headings with the 8th edition (Library of Congress 1975).
  • Standard thesaurus tags, USE, UF, BT, NT and RT were adapted by LCSH in 1987 and first used in the 11th edition (Library of Congress 1988). However, this change did not make LCSH a thesaurus. The semantic relations used by LCSH before the 11th edition (Library of Congress 1988) were see for USE; x for UF; xx for BT; xx and sa for RT; sa (general "see also" reference) for NT. As can be seen, there is no one-to-one correspondence between the old and new terms. The changes were first described by Library of Congress (1987) and were critically described and discussed by Dykstra (1988).
  • About the turn of the 20th century, libraries around the world began to abandon their local classification and indexing and instead rely on metadata imported via MARC-records from LC, OCLC and the Research Libraries Group. Hereby LCSH's influence (together with the Library of Congress Classification, LCC and the Dewey Decimal Classification, DDC) grew considerably at the expense of alternative systems.
  • FAST (Faceted Application of Subject Terminology) is a system that was derived from the Library of Congress Subject Headings (LCSH) from about 1998 in an attempt to modernize LCSH by applying → facet analytic and post-coordinated principles. Today FAST is not a system that has replaced LCSH, and although in use, it seems much less used than LCSH.
  • At the time of writing, LCSH is in its 44th edition (Library of Congress 2022), is freely available online, and contains 382,713 headings.

In order to illustrate the structure of LCSH, table 1 shows the entry about information science from 44th ed. (Library of Congress. 2022). The first line states that it may be subdivided geographically and that this subject heading is classified in the group Z665-Z718.8 in the LCC. This is followed by references to other terms, using the standard abbreviations from thesauri (BT, broader terms, RT, related terms, and NT, narrower terms). In other records, the thesaurus abbreviations USE and USED FOR are also applied to link subject headings considered synonyms.

Table 1: The Information science entry in LCSH
Information science (May Subd Geog) [1] [Z665-Z718.8]
  • Information literacy
  • Library science
  • NT
  • Agricultural informatics
  • Bioinformatics
  • Cheminformatics
  • Communication in information science
  • Documentation
  • Geomatics
  • Information organization
  • Information resources
  • Information retrieval
  • Information services
  • Information visualization
  • Medical informatics
  • Women in information science
  • LCSH is daily updated in the digital version available through Classification Web, and is adding approximately 4,000 headings each year. Libraries that participates the Subject Authority Cooperative Program may propose changes to LCSH.

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    3. Criticisms of LCSH

    There have been much criticism of LCSH over the years. There have been three general review articles summarizing this critique: Cochrane and Kirtland (1981), Shubert (1992) and Fischer (2005). Delgado and Stefancic (1989) also summarize criticism of the system [2]. The specific studies can be divided into two main groups: (1) Those that present criticism about LCSH's presentation of minority groups, and (2) those presenting criticism of the system as such, including its lack of usefulness, logic, sound principles, and necessary subject knowledge.

    (1) Examples of studies criticizing how minorities or underrepresented groups are represented in LCSH include, among other, Adler (2017), Aman (1980), Berman (1971; 1984), Dobreski, Hardesty and Nolan (2021), Lo (2019), Olson (2001) and Snow and Moulaison-Sandy (2022). Such studies rightfully point toward ethical problems in classification and indexing systems. However, sometimes criticism of this kind is accompanied by an implicit assumption that LCSH is in general a valuable system, that although these kinds of biases are important, they are not jeopardizing the system (if this were the case there would be no reason to address such bias). Hjørland (2012, 308) wrote:

    Olson (2001) examined the way in which LCSH were used to index some books in the field of gender studies, and found the indexing to be problematic. For example, the concept of 'voice' (in relation to the views of a minority) is not represented in LCSH. According to Olson's interpretation, this may be due to poor indexing of marginalized topics (as opposed to mainstream topics). My interpretation is unfortunately more pessimistic: I believe that this poor indexing is due to a lack of subject knowledge. The terms and relations in LCSH in relation to this field (gender studies) seem to be speculative and far away from the points of view that the literature in the field tries to put forward. This probably does not only apply to the views of minorities, which seem to be poorly represented by LC, but constitutes a general tendency that will also affect majority views.

    (2) A range of criticisms has been raised concerning the lack of principles and quality in the LCSH.

    • LCSH is a system of subject headings, but it is, as pointed out by Dykstra (1988) "disguised as a thesaurus". This has confused conceptions within LIS, but is has also, as demonstrated by Dykstra, caused problems for the function of LCSH. She decries the "chaos" surrounding LCSH and recommends "a shift in LCSH from an unruly to a rule-based system".
    • Concerning the geographical subdivision mentioned in Table 1, Furner and Hjørland (2023, 1269) wrote: "It is strange that SHs such as Information science, Documentation, Information organization, Library science, etc. are primarily subdivided geographically ("May Subd Geog"). For example, Cornelius' (1996) Meaning and Method in Information Studies (LCCN Permalink: https://lccn.loc.gov/96017290) is assigned the LC Subjects: Information science—Methodology, Hermeneutics and Information science—United States—Methodology. Why the term United States? The book is not about information science in the US (the author was professor in Dublin and honorary research fellow in University College London). It is about theoretical problems of information science/information studies in an international perspective". This problematic use of geographical subdivisions is not confined to information science, but is widespread in LCSH.
    • Many commentators have mentioned the silliness of LCSH. Wellisch (1981, 299-300), for example, wrote: "Here, too [in the ninth edition of LCSH], everything is still as it always was, perpetuating the inanities and absurdities that have accumulated since 1910 (or rather 1897, when work on LCSH began), and adding a few new ones, e.g., on the relative distance of islands from the nearest landmass (which is the decisive factor in naming them in either direct or indirect form)".

    A few studies examine how specific subjects are represented in LCSH:

    • Christ (1972) studied how concepts in the social sciences were represented in LCSH. He finds that there is a wide conceptual gulf between how social sciences understand themselves, and how they are understood in the way library science represents them in LCSH. This gulf complicates research and teaching in social science, and library science should make a philosophical change in order to meet the needs of the social sciences.
    • Furner and Hjørland (2023) examined how information science with knowledge organization are represented in LCSH, and how LCSH is used to classify books in this field. Among the findings were:
      • The term library and information science is not a subject heading (SH) in LCSH, nor is it a lead-in term for another SH. This is of importance both because the term is widespread in the LIS literature (and should therefore be represented due to LC's principle of → literary warrant) and because the term Information science (which is a SH) is ambiguous, and the use of Library and information science would help disambiguate this SH.
      • An expected symmetry between SH Information science and SH Information scientists cannot be observed. For example, when the SH Bibliographers is an NT to SH Information scientists, why then is SH Bibliography not an NT to SH Information science?
      • Two RTs for Information science (Information literacy and Library science) seem misplaced. Information literacy is a phenomenon studied by information science, and library science is a part of information science.
      • The term knowledge organization is not a SH in LCSH. Nor is it a lead-in term for another SH. LCSH does have an SH Information organization. As these two terms are mostly considered synonymous in the literature, the question is whether SH Information organization is also used by LC for knowledge organization? A look at scope note for SH Information organization indicates that this is the case. However, when it was examined how books about knowledge organization were indexed, SH Information organization was not consequently used, which implies that books about knowledge organization cannot be retrieved by using one or a few SH from LCSH.
      • Information science is not limited to books and libraries, but operates with a wide concept of documents, that includes records in archives and objects in libraries. In addition, a growing literature consider → libraries, archives and museums (LAM) as a combined field of study. All this seems also to have gone unnoticed in LC, as Archival studies and Museology have not been assigned as NTs for the SH Information science.
      • Etc. etc.
    • Larson (1991, 211) wrote: "Experience in catalog use may not necessarily imply that users have been 'conditioned' to avoid subject searches [searches using LCSH, not searches using title keywords], though such conditioning appears to be a likely result of gaining experience in catalog Library of Congress Subject Headings use, whether card or online catalog. We would suggest, as a hypothesis for further study, that individual users' experiences of subject search failure and information overload lead them to reduce their use of the subject index and to increase their use of alternate means of subject access, such as title keyword searching and shelf browsing following a known item search". Although Gross and Taylor (2005) provided a response to Larson defending subject headings, Furner and Hjørland's (2023) study supports Larson's findings.

    Have there been defenses of LCSH, attempts to refute the criticism? To our knowledge, the Library of Congress itself has never done so. (One among other indications that the activities of LC are not research based?) Some others have defended LCSH, but in our opinion with extremely weak or strange arguments.

    Studwell (1990) intended his book to fill the lack of books about philosophical issues and theoretical principles of the LCSH and presented 32 "principles" relating to this system. However, it consists of 32 claims and the author's suggestions for improving the system rather than principles or philosophical and theoretical analyses on which the system is based. The first "principle" was (p. 11–12): "The Library of Congress subject heading system, though far from perfect, is a work of collective, cumulative, and increasing genius; it should not be discarded in favor of less-established and unproven alternatives". This quote does not state a principle on which LCSH is based. It just state an unsupported flattering. Studwell's view of LCSH as being a work of genius based on philosophical principles is in stark contrast to the views of other researchers.

    Delgado and Stefancic (1989), after having summarized criticisms of LCSH, wrote:

    Still, many staunchly defend the Library of Congress system [FN24] [3]. These defenders point out that the Library of Congress Subject Headings was never intended to be an all-inclusive set of categories. Rather, it was intended to enable the Library of Congress to deal with one single collection, its own [FN25]. Moreover, when the Library of Congress adopted the categories, they were adequate for the Library's then small collection. Most libraries, even those with specialized collections, chose to adopt the Library of Congress headings, and the Library maintained the essentials of the system even as the collection grew. As a result, the Library of Congress system extended far beyond the task for which it was originally designed [FN26]. Finally, defenders add that it is reasonable for the Library to take into account the cost of changes, especially when these changes will be multiplied at other libraries throughout the United States, and that the Library does add new categories when the need for them is shown [FN27].

    Again, these are not arguments that LCSH are doing a good job. These are excuses for why the system is as it is. The last comment, that the Library does add new categories when the need for them is shown, is not demonstrated, just claimed — and in strong opposition to the findings of Furner and Hjørland (2023).

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    4. Conclusion

    Information science with knowledge organization was institutionalized as a research field and an academic field of study about one hundred years ago. It is important that research influences practical information work (e.g., the design of controlled vocabularies). Hjørland (2023, Section 2) wrote: "For two reasons it is a problem if systems and processes used in practice are obsolete [or simply bad] from a research perspective: 1. it may imply that research-based education is less relevant for practice because practice ignore new systems not in use; 2. it may imply that education reflecting current practices may not have a proper academic level and may be less relevant for tackling new developments".

    We listed in the introduction no less than six textbooks devoted to the LCSH, which is just a little part of the huge number of articles and book chapters about this system used in courses in knowledge organization. The emphasis on LCSH is understandable given its huge availability in library databases. It is also, however, a problem that such a poor system is what the students learn about, especially if they learn that it is a system that is beneficial for the users.

    Markey and Knott (2023) is a textbook on online searching. Chapter 6 introduces CVs, including LCSH. In principle well and good. There is a danger, however, that students with this book learn that CVs are good and to be trusted, while they need to learn to be critical. One misses examples comparing different search strategies, including ones, in which — after the words of Larson (1991) — users should "reduce their use of the subject index [CV] and [...] increase their use of alternate means of subject access".

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    1. See Section 3 for a critical comment about the geographical subdivision.

    2. Citing Dwyer (1986, 3) and Scott (1988, 64), Delgado and Stefancic (1989) concluded: "Impatience with the Library of Congress Subject Headings has led at least one other library system, that of Minnesota's Hennepin County, to produce its own subject heading list and make it available to other libraries. Hennepin's subject headings have been called both more current than Library of Congress Subject Headings and more sensitive to social and cultural changes".

    3. FN24, FN25, FN26, and FN27, endnotes in Delgado and Stefancic (1989), are omitted in the present article.

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    Version 1.0 published 2023-09-19

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