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 exarnined 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 ana1ysis as the base for corre1ation analysis. The results show that there are four cluster types, including techno1ogica1 affiliated, techno1ogica1 competitor corre1ated, commercia1 collaborated and techno1ogica1 iso1ated.