Field-Normalized Citation Impact (MNCS)

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.