Properties of the USPTO patent citation network: 1963–2002

The network of patent citations is a collection of clumps of citations between closely related patents, with the largest clumps being defined by patent technology categories. The exchange of citations between these groups evolves over time and reveals technological trends. By using USPTO data and considering the evolution of backwards- and forwards-, and intra- and inter-citations, conclusions about the generality, originality, and productivity of patents and technology categories can be drawn.