To uphold our commitment to responsible metrics, we have created ‘data notes’ for specific searches in Overton. These notes inform you about possible limitations in our data for your chosen search context.
We rank ‘data notes’ into three categories by priority. This article will list all the ‘low priority’ or green data notes along with an interpretation.
Your search contains documents from before 2015
Overton started in 2019 and collects as far back as it can, but not all policy documents have been put online, and many have disappeared as government agencies close, merge, think tanks wind down and so on.
This might be an issue if you’re trying to detect trends over a long period of time, as we have a smaller proportion of all policy published in older years, and that proportion may not be adequately representative.
As a rule of thumb back to 2015 is fine, 2009 – 2015 is OK as long as you control for sources, and pre 2009 requires careful interpretation.
Be especially cautious with data from before 2009, as it may not accurately reflect their complete body of work. Use care when making measurements, comparisons, or benchmarks with this data.
You’re using a filter that uses journal subjects data
Overton gets the subject areas for academic journals from Scimago, which in turn is derived from data from Elsevier’s Scopus platform.
The subject areas are assigned at a journal level, not an article level: it’s possible that a journal’s primary subject doesn’t describe every article published in it.
Some large journals like PLoS One, Nature and Science have “multidisciplinary” as their journal subject.
Make sure to search in different but related subject areas, using DOI and other identifiers to find more results.
Every policy source in Overton has exactly one primary country associated with it. This is usually where the source’s headquarters is located.
Intergovernmental and European Union institutions are considered special cases. EU agencies and institutions have “EU” in their country field and intergovernmental institutions have “IGO”.
You’re using a filter that uses the primary country associated with an institutional affiliation
Using other filters can help you capture these additional outputs.
You’re using the published by filter
Overton gets the publisher name for each scholarly paper or other output from Crossref.
That data comes from the publishers themselves.
The vast majority of the time it is accurate. However, it isn’t always consistent or updated. Journals often move publisher, or publishing companies merge, and publishers sometimes change names. In all these cases the publisher name on each article is the one that was true at its time of publication.
If you know about publisher changes or name changes, you can also narrow your search by date or include multiple publisher names.