手法を比較

	Price Index (Citation Recency)	Immediacy Index
分野	計量書誌学	計量書誌学
系統	Process / pipeline	Process / pipeline
提唱年	1970	1972
提唱者	Derek J. de Solla Price	Eugene Garfield (ISI / Journal Citation Reports)
種類	Reference-recency pipeline	Same-year citation-rate pipeline
原典	Price, D. J. de Solla (1965). Networks of scientific papers. Science, 149(3683), 510-515.	Garfield, E. (1972). Citation analysis as a tool in journal evaluation. Science, 178(4060), 471-479.
別名	Price's Index, Citation Recency Index, Share of Recent References, Research-Front Index	Journal Immediacy Index, Same-Year Citation Rate, Current Citation Rate, Year-of-Publication Citation Index
関連	3	3
概要	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.	The Immediacy Index measures how quickly a journal's articles are cited by counting the citations they receive in the very year they are published. Eugene Garfield, who created the Science Citation Index and the impact factor, introduced the immediacy index as part of the Institute for Scientific Information's journal-evaluation methodology and described it in his landmark 1972 Science paper on citation analysis as a tool in journal evaluation. While the impact factor averages citations over a two-year window, the immediacy index uses a zero-year window: it divides the citations made in a given year to that year's articles by the number of citable items published that year. A high immediacy index means a journal's work is picked up almost immediately, the signature of a fast-moving, frontier field or of journals that publish hot, rapidly cited material. It is a measure of citation speed rather than of total impact.