手法を比較

	Crown Indicator (CPP/FCSm)	Field-Normalized Citation Impact (MNCS)
分野	計量書誌学	計量書誌学
系統	Process / pipeline	Process / pipeline
提唱年	1995	2011
提唱者	Henk F. Moed, R. E. De Bruin & Th. N. Van Leeuwen (CWTS Leiden)	Ludo Waltman, Nees Jan van Eck & colleagues (CWTS Leiden)
種類	Field-normalized citation impact indicator (ratio of averages)	Field-normalized citation impact indicator
原典	Moed, H. F., De Bruin, R. E., & Van Leeuwen, T. N. (1995). New bibliometric tools for the assessment of national research performance: Database description, overview of indicators and first applications. Scientometrics, 33(3), 381-422.	Waltman, L., van Eck, N. J., van Leeuwen, T. N., Visser, M. S., & van Raan, A. F. J. (2011). Towards a new crown indicator: Some theoretical considerations. Journal of Informetrics, 5(1), 37-47.
別名	CPP/FCSm, old crown indicator, Leiden crown indicator, CWTS crown indicator	Mean Normalized Citation Score, MNCS, normalized citation impact, new crown indicator
関連	3	3
概要	The crown indicator, written CPP/FCSm, was the field-normalized citation impact measure developed at the Centre for Science and Technology Studies (CWTS) in Leiden and described by Moed, De Bruin, and Van Leeuwen in 1995. It compares a unit's observed citation rate with what would be expected given the fields, document types, and years in which it published. Specifically, it divides the citations per publication (CPP) by the mean field citation score (FCSm), forming a ratio in which a value of 1 marks performance exactly at the field average. For more than a decade it was CWTS's flagship indicator, until Waltman and colleagues showed in 2011 that its ratio-of-averages construction had statistical drawbacks and proposed the MNCS as a successor.	The Mean Normalized Citation Score (MNCS) is the field-normalized citation impact indicator developed at the Centre for Science and Technology Studies (CWTS) in Leiden and articulated in Waltman and colleagues' 2011 paper on a new crown indicator. Raw citation counts cannot be compared across fields, because a molecular biology paper and a mathematics paper accumulate citations at vastly different rates, and older papers have had more time to be cited. The MNCS removes these distortions by dividing each paper's citations by the average citations of comparable papers in the same field, document type, and publication year, then averaging these normalized ratios. A value of 1 means performance exactly at the world average for the relevant fields, while values above or below 1 indicate above- or below-average impact.