Compare methods

	Citing vs Cited Half-Life Asymmetry	Price Index (Citation Recency)
Field	Bibliometrics	Bibliometrics
Family	Process / pipeline	Process / pipeline
Year of origin	1960	1970
Originator	Robert E. Burton & R. W. Kebler; Ronald Rousseau	Derek J. de Solla Price
Type	Two-sided aging-comparison pipeline	Reference-recency pipeline
Seminal source	Burton, R. E., & Kebler, R. W. (1960). The "half-life" of some scientific and technical literatures. American Documentation, 11(1), 18-22.	Price, D. J. de Solla (1965). Networks of scientific papers. Science, 149(3683), 510-515.
Aliases	Citing-Cited Half-Life Comparison, Synchronous vs Diachronous Half-Life, Reference and Citation Age Asymmetry, Journal Temporal Profile Analysis	Price's Index, Citation Recency Index, Share of Recent References, Research-Front Index
Related	3	3
Summary	A journal has two half-lives, and comparing them reveals its temporal personality. The cited half-life measures the median age of the articles the journal is cited for, capturing how long its own work stays useful. The citing half-life measures the median age of the references the journal's articles make, capturing how far back its authors reach. Burton and Kebler's 1960 half-life framework supplies the median-age machinery for both, and Ronald Rousseau's work on the temporal structure of journal citations underscores that incoming and outgoing citation streams age differently. When the two half-lives diverge, the asymmetry is informative: a journal whose work is cited for many years but which itself cites only recent literature sits at a fast research front yet produces durable results, while the reverse profile marks a synthesizing or archival journal. The asymmetry is the gap between how a journal is used and how it uses the literature.	The Price Index measures how strongly a field draws on recent literature by computing the percentage of its references that point to work published within the last few years. Derek de Solla Price, the founder of modern scientometrics, observed that the sciences differ sharply in how immediate their referencing is: hard sciences cite a tight cloud of recent papers at the research front, while humanities scholarship cites a long, even spread of older works. In his 1965 Science paper on the networks of scientific papers he documented this concentration of references on recent years, and in his 1970 essay distinguishing hard science, soft science, technology, and nonscience he formalized the index that now bears his name. Defined as the share of references no older than about five years, the Price Index is a citing-side companion to obsolescence measures: where the cited half-life looks at how the literature ages, the Price Index looks at how recency-focused the citing behavior is.