Grey literature is defined as "information produced on all levels of government, academia, business and industry in electronic and print formats not controlled by commercial publishing i.e., where publishing is not the primary activity of the producing body."1 A major advantage of grey literature is that because information is not published through commercial publishing channels (e.g., journals) the information can be published faster. This is especially important with emerging issues. Grey Literature is literature that is not published through traditional means and is often excluded from traditional academic databases.
Grey literature includes data from many different sources with varying levels of reliability and review. Government reports, including statistical reports from agencies such as AHRQ, the CDC, and CMS as previously described in this training, are considered grey literature. Government reports are widely considered valid and reliable sources.
Dissertations, conference proceedings, newsletters, and blogs are also considered grey literature. One would expect a dissertation, which has undergone numerous reviews before a doctoral student can graduate, to be of a higher quality than a newsletter, which has little to no peer review. However, both dissertations and newsletters are considered grey literature.
Examples of Grey Literature include, but are not limited to,
Sources of Grey Literature may be located in commercial databases, websites and/or university repositories.
"The intent of an evidence synthesis is to synthesize all available evidence that is applicable to your research question. There is a strong bias in scientific publishing toward publishing studies that show some sort of significant effect. Meanwhile, many studies and trials that show no effect end up going unpublished. But knowing that an intervention had no effect is just as important as knowing that it did have an effect when it comes to making decisions for practice and policy-making. While not peer-reviewed, grey literature represents a valuable body of information that is critical to consider when synthesizing and evaluating all available evidence."
Source: https://guides.library.cornell.edu/evidence-synthesis/gray-literature
