A Comparative Study of Linkage Indexes: Co-assignee, Reciprocal Citation, Patent Coupling and Co-patent

Four indexes including co-assignees, reciprocal citation, patent coupling and co-patent were examined in this study to reveal the meanings of the correlations generated via different citation linkages. This study includes 6,274 genetic engineering patents, and 16 primary assignees identified by Bradford model analysis as the base for correlation analysis. The results show that there are four cluster types, including technological affiliated, technological competitor correlated, commercial collaborated and technological isolated.