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The Informetric Laws

Figure 9.5 Growth of the number of Internet hosts. Origin: www.isc.org; redrawn with
permission.

Egghe (1993a), Egghe, Rao, and Rousseau (1995), and Egghe and
Rousseau (2000), that growth increases synchronous obsolescence, but
decreases the diachronous one.
We finally note that general growth, aging and production models,
described via differential equations, are presented in Vitanov (2016).

9.3 TWO-DIMENSIONAL INFORMETRICS
9.3.1 General IPPs

Two-dimensional informetrics studies the relation between two of the
“informetric objects” mentioned in the part on one-dimensional infor-
metrics. In this context these things are referred to as sources and items:
sources “produce” or “have” items. Egghe (1990, 2005) refers to such
relations as Information Production Processes, in short IPPs. For example,
authors, as sources, and the number of articles (co)-authored by them as
items. Usually one restricts investigations to a given domain and some-
times also to a specific time period. An IPP can be represented as in
Fig. 9.6: S represents the set of sources; I represents the set of items;
s j represents source j connected via function f to its set of items I j .
Examples of IPPs
• Authors and their articles.
• Journals and their articles.