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Full-Text Coverage Ratios

Matthew Goddard, Iowa State University
Adapted by Sian Brannon, University of North Texas

The basic idea behind full-text coverage ratios (FTCRs) is that the ratio between held items and total items indexed in a discovery service is an interesting and actionable number that can shed light on the relative strength of holdings in particular subject areas. This number can be calculated from the total number of items returned by two discovery-layer searches that are identical in every way but one: one is limited to full-text items, the other is not limited; i.e., the other is “expanded.”The questions that FTCRs can help answer depend on your confidence in the comprehensiveness of your discovery layer’s search index. If confidence is high, you would be able to say, “We’re able to provide roughly X% of what has been published in this area.” If confidence is low, you would still be able to say, “We’re able to provide roughly X% of what we have indexed in this area.”

Full-text coverage ratios can be determined for any subject area that can be fairly represented by a discovery-layer search: for example, they might correspond to a campus unit, a degree program, a course, or a particular research project. In every case, the first step is to define a representative search for that subject area. Since FTCRs are ratios, the searches do not need to be perfectly accurate and comprehensive of their subject area, only representative.

For example:

FTCR scope Subject area Example search syntax
Campus unit Life sciences biolog* OR botan* OR ecolog* … [etc.]
Degree program Biology biolog*
Course Plant Metabolism “plant metabolism”
Research project Isotope labeling experiments “isotope labeling” OR “isotope labelling”


Other search features might be used to further tailor the scope of investigation. For example, for the projects listed above, the scope might be defined as peer-reviewed articles published in the last five years. The FTCR can be calculated for each row by dividing the total number of items returned by two searches run according to these parameters using the syntax in column C, one limited to full-text available results, the other not limited.

Some example applications:

  • Prior to negotiations for journal package X, calculate FTCRs for relevant disciplines before and after removing the package from a full-text filter (using a test/sandbox profile).
  • After acquiring a new journal package Y, calculate FTCRs for relevant disciplines before and after adding the package to demonstrate or test its value.
  • Calculate FTCRs for all degree programs to determine which are in most need of increased support, or which are well positioned to absorb budget reductions.

Adapted with permission from:

Goddard, M. (2020, June 10). Full text coverage ratios: A simple method of article-level collections analysis.  NASIG Conference. 

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