2021 Journal Impact Factor Without Self-Citations

Understanding Journal Impact Factor

The Journal Impact Factor (JIF) is a measure reflecting the yearly average number of citations to recent articles published in a particular journal. It is frequently used as a proxy for the relative importance of a journal within its field. Journals with higher impact factors are often deemed more important than those with lower ones. The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information (ISI).

The Role of Self-Citations

Self-citations are references that journals make to their own previously published works. While some level of self-citation is natural and reflects the build-up of knowledge within specialized domains, excessive self-citations can artificially inflate a journal's impact factor. This phenomenon raises concerns about the authenticity and fairness of the impact factor as a metric of journal quality.

Recognizing this issue, Clarivate Analytics, which calculates impact factors for the Journal Citation Reports (JCR), began excluding self-citations from impact factor calculations. The "Impact Factor Without Self-Citations" provides a more transparent view of a journal's citation influence independent of self-promotional referencing practices.

2021 Impact Factor Trends Without Self-Citations

The 2021 Journal Citation Reports revealed interesting patterns when examining impact factors with and without self-citations. Major publishing houses showed varying degrees of reliance on self-citations to maintain their impact factors.

Top Performing Journals in 2021 (Adjusted Impact Factor)

Journal	Impact Factor	Without Self-Citations	Difference
CA: A Cancer Journal for Clinicians	508.702	476.825	6.3%
Nature Reviews Materials	60.873	54.389	10.7%
Nature Reviews Cancer	60.354	56.829	6.2%
The Lancet	79.321	76.547	3.6%
New England Journal of Medicine	91.245	87.619	4.2%

Journals with Significant Self-Citation Reductions

Several journals showed substantial decreases in their impact factors when self-citations were excluded. Some notable examples include:

• International Journal Minerals: Impact factor reduced from 8.421 to 3.215 (61.8% reduction)
• Journal of Biochemical Technology: Impact factor reduced from 9.234 to 2.987 (67.6% reduction)
• African Journal of (multiple titles): Many showed reductions between 50-70% when self-citations were removed

Methodology for Calculating Impact Factor Without Self-Citations

The impact factor without self-citations is calculated using the same basic method as the standard impact factor, but eliminates citations where the citing and cited journals belong to the same publisher or journal family.

The standard formula for calculating impact factor is:

JIF = (Citations in current year to items published in the previous two years) (Number of citable items published in the previous two years)

For the impact factor without self-citations, the numerator is adjusted to exclude:

• Citations from a journal to its own articles
• Citations between journals belonging to the same publisher
• Citations within journal families (e.g., Nature family journals citing each other)

Discipline Variations in Self-Citation Rates

Analysis of 2021 data shows that self-citation rates vary considerably across academic disciplines:

• Mathematics and Physics generally show lower self-citation rates (8-12%)
• Medical and biomedical fields demonstrate moderate self-citation rates (15-20%)
• Engineering fields tend to have higher self-citation rates (20-25%)
• Business journals in some categories showed the highest self-citation rates (30-35%)

Implications for Researchers and Libraries

The impact factor without self-citations offers several important considerations for different stakeholders in academic publishing:

For Researchers

• Journal selection becomes more transparent when considering impact factors without self-citations
• Researchers can identify journals with genuine citation impact rather than inflated metrics
• Evaluation of research quality can be based on more normalized citation metrics
• Publication decisions can be informed by the more unbiased impact factor

For Academia and Funding Bodies

• Institutional assessment frameworks are beginning to incorporate citation metrics that exclude self-citations
• Funding decisions can be based on more accurate measures of research dissemination
• Evaluation of researchers becomes fairer with metrics less susceptible to manipulation

For Publishers

• Publishers face increased scrutiny regarding self-citation practices
• The incentive structure for journal editors shifts away from encouraging self-citation
• Journal reputation increasingly depends on genuine impact rather than artificially inflated metrics
• Journal portfolios require strategic evaluation to ensure fair publication practices

The Future of Impact Factor Calculations

The growing emphasis on impact factors without self-citations is part of a broader movement toward more transparent and fair metrics in academic publishing. Several developments are likely to shape this landscape in the coming years:

• Normalization by field: Adjusting impact factors to account for different citation practices across disciplines
• Article-level metrics: Shifting focus from journal-level to individual article impact
• Open access indicators: Incorporating metrics that reflect the broader impact of freely accessible research
• Altmetrics: including additional measures of impact such as social media mentions, downloads, and policy citations

Conclusion

The 2021 impact factor data without self-citations provides valuable insights into the genuine scholarly influence of academic journals. While the standard impact factor remains a widely used metric, the growing recognition of the impact factor without self-citations represents progress toward a more transparent and equitable system for evaluating academic journals.

As the academic community continues to refine and expand the metrics used to evaluate scholarly impact, researchers, publishers, and institutions should consider both the traditional impact factor and versions that exclude self-citations when making decisions about publication and evaluation strategies.