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Evidence Synthesis: Systematic Reviews, Scoping Reviews, Etc.

What is Grey Literature

Grey literature refers to a diverse array of information that is generated outside of conventional publishing and distribution methods, often lacking proper representation in indexing databases (i.e. search engines). 

Grey literature can include unpublished surveys, government reports and publications, conference proceedings and abstracts, policy briefs and white papers, theses and dissertations etc. For a more extensive list, check out the following site:

The approach to including and searching for grey literature will vary significantly depending on the nature of your research question, necessitating a tailored strategy that aligns with the specific characteristics associated with your area of investigation.

Finding Grey Literature

Check government websites, policy institutes, and non-governmental organization (NGO) platforms for reports, policy papers, and research studies related to your topic of interest. 

Explore the repositories of academic institutions, universities, and research organizations, which often house theses, dissertations, technical reports, and other unpublished research materials.

Look for conference proceedings and abstracts from academic conferences, as these can often contain valuable research findings and studies that have not yet been formally published.

Where to find conference proceedings: 

Visit the websites of professional associations and societies within your field, as they may publish reports, white papers, and other forms of grey literature.

Preprint servers where researchers may share preliminary findings, unpublished manuscripts, and other forms of grey literature. Following are some helpful preprint servers in social sciences:

When to stop searching grey literature

Knowing when to stop searching for grey literature can be a nuanced decision and may depend on several factors. Here are some considerations to help you determine when it might be time to conclude your search:

  • Relevance of Sources: Assess the relevance of the sources you've found. If the information aligns well with your research goals and contributes meaningfully to your work, it may be a sign that you've covered the necessary ground.
  • Coverage of Perspectives: Consider whether your search has covered a diverse range of perspectives and sources. If you have obtained a comprehensive understanding of the topic, additional searching may yield diminishing returns.
  • Search Exhaustion: If you find that you are repeatedly encountering the same sources or not discovering new and valuable information, it may be an indication that you've exhausted the available grey literature on your topic.
  • Consultation with Peers or Experts: Seek feedback from peers, mentors, or subject matter experts. If others in your field believe you have covered the relevant literature, it may be time to conclude your search.
  • Diminishing Returns: If additional searches consistently yield information of diminishing relevance or significance, it may be a sign that further efforts are not productive.

Read Kastner et al., 2007 to read more on "stop searching" strategy in systematic reviews. 

 

Grey Literature: To include or not to include ... that's the question!

Advantages of including grey literature

  • Broader Perspective
  • Grey literature can provide a more comprehensive and holistic view of the research landscape, incorporating diverse perspectives and insights that may not be available through traditional published sources.
  • Current and Timely Information
  • Grey literature often includes up-to-date information, offering the latest research findings, policy developments, and other relevant data that may not have been formally published yet.
  • Policy and Practice Relevance
  • Grey literature frequently includes policy briefs, reports, and white papers, providing practical implications and applications that can be directly relevant to policy-making, practice, and decision-making processes.
  • Diverse Data Types
  • Incorporating grey literature enables you to utilize various data types, such as technical reports, conference proceedings, and working papers, which can contribute diverse perspectives and methodologies to your research.
  • Filling Knowledge Gaps
  • Grey literature can help fill knowledge gaps and address research questions that may not have been adequately covered by published academic literature, offering a more nuanced understanding of the research topic.
  • Reducing Publication Bias
  • Including grey literature can reduce the impact of publication bias by incorporating findings and insights that may not have met the stringent publication criteria of traditional peer-reviewed journals.

Limitations of Grey Literature 

  • Quality Control Challenges
  • Grey literature may lack the rigorous peer-review process associated with traditional academic publishing, leading to potential concerns about the quality and reliability of the information. Some forms of grey literature may be challenging to access, as they are often not widely disseminated or indexed, making it difficult to verify their authenticity and credibility.
  • Variability in Reporting Standards
  • Grey literature sources may exhibit a wide range of reporting standards and methodologies, making it crucial to critically evaluate and assess the credibility of the information presented.
  • Risk of Outdated Information
  • Some grey literature, especially in rapidly evolving fields, may contain outdated or superseded information that could impact the accuracy and relevance of your literature review.
  • Lack of Citations and Attribution
  • Grey literature often lacks proper citations and attributions, which can make it challenging to verify the original source and trace the information back to its primary author or organization.
  • Considering these limitations, it is essential to exercise caution when integrating grey literature into your review, ensuring that you critically evaluate and validate the credibility and relevance of the sources to maintain the integrity of your research.