Time series of outgrow indices

The outgrow index measures to which extent an article outgrows – in terms of citations – the references on which it is based. In this article, three types of time series of outgrow indices and one outgrow index matrix are introduced. Examples of these time series are given illustrating the newly introduced concepts. These time series expand the toolbox for citation analysis by focusing on a specific subnetwork of the global citation network. It is stated that citation analysis has three application areas: information retrieval, research evaluation and structural citation network studies. This contribution is explicitly placed among structural network studies.

► Zunde's classification of application areas for citation analysis is adapted to later developments in the field. Hence we propose the following classification: (1) information search and retrieval; (2) citation-based research evaluation, and (3) structural studies of citation networks, including historical developments of a topic or field.
► The outgrow index, characterizes publications by focusing on their specific position in a local subnetwork of the universal citation network. It is a structural indicator, explicitly seen as belonging to the third application area mentioned above.
► Diachronous and synchronous time series of outgrow indices are defined, including a two-dimensional dia-synchronous one, and practical examples are provided.