Bibliometric Indicators

Bibliometric indicators are numerical measures derived from scientific publications and the citations they receive. They help describe research output and scholarly influence at the level of researchers, institutions, journals or countries, but do not directly establish the quality or social value of research.

Major indicators and what they measure

Different indicators measure different aspects of performance, so they should not be treated as interchangeable.

• Publication counts measure the volume of research output recorded in a selected database; they do not establish its originality or quality.
• Citation counts record how often publications are referenced by other publications, providing a proxy for scholarly influence rather than a direct measure of correctness.
• A researcher has an h-index of h when h of their publications have each received at least h citations; it combines publication output and citation performance.
• The Journal Impact Factor is a journal-level citation indicator based on citations in a given year to content published during the preceding two years; it is not a measure of an individual article's quality.

Role in research evaluation

Bibliometric indicators provide a systematic way to examine large bodies of research that would be difficult to assess through individual reading alone.

• They support benchmarking of publication output and citation performance across institutions or countries when comparable data and methods are used.
• Publication and co-authorship patterns help identify research specialisations, emerging areas and collaboration networks.
• They can inform funding and institutional assessment by supplementing evidence about research activity and influence.

Limitations and risks

An indicator's meaning depends on the database, subject area, publication type and time period being examined.

• Citation practices differ across disciplines, making raw citation comparisons across fields misleading.
• Older publications have had more time to accumulate citations, while career length affects cumulative researcher-level indicators.
• Database coverage can underrepresent local-language publications, books and research addressing regional needs.
• Citations may reflect criticism or self-citation; publication-centred measures also miss outcomes such as practical applications and social benefits.

Principles of responsible use

Field-normalised indicators compare citation performance with an appropriate disciplinary benchmark. Bibliometrics should support, not replace, expert peer review, with assessment also considering originality, methodological rigour and societal relevance.

• Evaluators should disclose data sources and counting methods, use multiple indicators, and avoid judging researchers by journal metrics alone.