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Relative impact index
Definition
The two-year relative impact index (expressed as a positive number) is defined as:
The citation share received by the publications of an actor (institution, country, etc.) over a specified time (for example two years) within a given frame of reference (world, for example), proportional to its share of publications within the same frame of reference.
N.B. The relative impact index is normalised so that at the scale of the frame of reference the indicator is equal to 1. When the indicator is greater than 1 it signifies that the actor enjoys a greater visibility than the average for all actors in the frame of reference (or less than average if the indicator is less than 1).
Example
Table 1-3-50
France : scientific publications – world share of publications, two-year citation share, and two-year impact index for all fields taken together, over a long period (1993 – 2004).
- Click to enlarge (taken from the OST Report – 2006 edition)
Interpretation: In 2004 the two-year impact index for France at the world level was 0.94 – lower, that is, than average world impact which by construction is 1. Overall, France's impact improved over the period, moving from 0.91 in 1993 to 0.94 in 2004.