NPCN: A New Method of Patent Citations Normalization Based on Ego Patent Citation Networks

Abstract

[Purpose/Significance] The number of citations received by patents is an important indicator to measure the influence of patents. Since the citation potential of patents varies greatly by disciplines and publication years, the number of citations received by patents needs to be normalized before cross-disciplinary comparison and cross-year comparison. [Method/Process] Based on ego patent citation network, we constructed a new method, NPCN, to normalize patent citations. Besides, we took patents granted from 2005 to 2010 of 3D printing indexed in Dimensions to verify the effective of NPCN. Specially, we divided these patents into different disciplines with Fields of Research (FoR) and compared the distribution of patent citations and NPCN of patents in different disciplines and publication years. Besides, we also selected the mean method、reference patents method、Z-score method and NPCN methods and compared them with each other in correlation with patent citations. [Results/Conclusions] Patents of 3D printing are categorized into 22 FoR. And it is different between patents in the number of citations. After normalized, the difference between patents in different disciplines and publication years is smaller and a normalized citation distribution is shown. In correlation with patent citations, NPCN is less correlated with patent citations than other normalized methods.

Keywords

• ego citation networks