The external rhythm of an actor in science: New indicators for the science of science

TL;DR

This paper introduces the external rhythm indicator, a new citation-based metric that enables comparison of individual actors' citation performance across different publication years and within collectives.

Contribution

It defines and explores the external rhythm of an actor, extending previous internal rhythm measures to allow comparisons across actors and collectives using citation ratios.

Findings

External rhythm enables cross-year citation comparison.

It allows comparison of individual actors with their collective.

The proposed summary average ratio provides a concise performance measure.

Abstract

When calculating citation indicators, whether it is the total number of received citations or the average citations per paper, we always face the same problem. Namely, that papers published in different years have varying citation potential. Hence, strictly speaking, their citations cannot be compared. In a former study, we created a new indicator called the internal rhythm indicator of an actor. The internal rhythm indicator makes it possible to compare the citation performances among different publication years, but it is only valid within the actor based framework. In this study, we define, create, and explore the external rhythm of an actor, which is also a sequence of ratios of observed citations to expected citations. The essential difference between internal rhythm and external rhythm lies in the way they are created and hence in the point of view taken to study an actor. The former is created based on its own publication-citation matrix, while the latter is based on two publication-citation matrices. One is the same as the former. The other one is a publication-citation matrix of a collective, which includes the actor under study. The external rhythm of an actor is a citation-based indicator of research that can be used to compare not only the citation performance of an actor with that of the collective the actor is part of, but also to compare two or more actors within the same collective. We further propose a summary average of ratios indicator.