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When it comes to publishing scientific research, one concept that is frequently discussed is journal impact factor (IF). For researchers, especially those looking for a journal to publish in, understanding what this metric is (and more importantly what it is not!) is crucial. Let’s explore its significance and discuss some common criticisms.

What is an Impact Factor?

Simply put, the impact factor is a measure of how often articles in a specific journal are cited over a particular period. Calculated annually by Clarivate Analytics, the impact factor is determined by dividing the number of citations in a given year by the total number of articles published in the previous two years.

For instance, if articles published in a journal during 2021 and 2022 received 100 citations in 2023, and the journal published a total of 50 articles in those two years, the impact factor would be 2.0.

What is a 5-Year Impact Factor?

While the standard impact factor considers citations over a two-year period, the 5-year impact factor provides a broader view by extending this period to five years. This metric can offer a more stable and comprehensive picture of a journal’s influence, as it accounts for citations that might accumulate over a longer timeframe.

Criticisms of Impact Factor

Despite its widespread use, the impact factor has faced significant criticism. Here are some common points of contention:

1. Skewed by Review Articles: Review articles typically receive more citations than original research articles. Journals that publish a higher number of reviews often have inflated impact factors, which may not accurately reflect the quality or influence of their original research.
2. Quality vs. Quantity: There’s a growing consensus that a higher impact factor does not necessarily correlate with the quality of the work published. High-impact journals might still publish papers with significant limitations, including poor adherence to reporting guidelines.
3. SPIN and Overinterpretation: High-impact journals are not immune to issues like SPIN or the overinterpretation of research findings. Our study (McGrath et al.) highlighted that even in prestigious journals, there's a tendency to overstate the implications of research, which can mislead readers and affect the perceived significance of studies.
4. Disciplinary Variations: Impact factors vary widely between disciplines, making it an uneven metric. For instance, biomedical sciences tend to have higher impact factors compared to social sciences, which can misrepresent the relative importance of research across fields.

Emerging metrics to demonstrate Journal ‘Impact’

Despite its limitations, journal impact factor has become an important metric for researchers to consider as it often (even if inappropriately) is tied to promotion, awards, and recognition in the academic community. Given its limitations, alternative journal metrics have been developed each with their strengths and limitations:

1. Eigenfactor Score: This metric gives more weight to citations from highly cited journals. It attempts to consider the influence of a journal within the broader scientific community and excludes journal self-citations.
2. Article Influence Score: Derived from the Eigenfactor Score, this metric measures the average influence of a journal's articles over the first five years after publication, providing a more balanced view of impact over time.
3. Relative Citation Ratio (RCR): Developed by the US National Institutes of Health (NIH), the RCR normalizes citations by comparing them to a field-specific reference set. This metric accounts for differences in citation practices across disciplines and aims to provide a more accurate measure of an article's impact.
4. SCImago Journal Rank (SJR): This metric uses a sophisticated citation weighting scheme and eigenvector centrality to rank journals. It assigns different values to citations based on the importance of the citing journals, offering a more nuanced view of journal impact.
5. h-index for Journals: Similar to the h-index used for individual researchers, this metric measures the productivity and citation impact of a journal's publications. It can complement the impact factor by providing additional insights into a journal's influence.

Focusing on Impact not Impact Factor

Perhaps the most important takeaway for researchers is to focus on impact, not the impact factor. This underscores the fact that research can improve patient care and change an entire field regardless of what journal it is published in. The impact of a study is more influenced by factors like open access publication status, knowledge translation efforts (e.g., conferences, social media), and the collaborations it builds, rather than the prestige of a journal. Ultimately, meaningful research is defined by its real-world contributions, not just its citation metrics.

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