U.S. Net and Total Patent Citation Flows, 1963-2002
U.S. patents are classified into technology categories at a number of different levels. At the one-digit level there are six categories, and at the two-digit level there are 36 categories. On application, every patent is required to cite previous art. The citations to other patents are a patent's "up-citations", while the patents citing a patent are its "down-citations". The total, net, in-flow, and out-flow of citations between categories provides insight into trends in technological innovation.
This Demonstration uses the patent citations datasets compiled by B. H. Hall, A. B. Jaffe, and M. Tratjenberg (2001) comprising more than 3 million U.S. patents (and more than 16 million citations) granted between January 1963 and December 2002. This Demonstration allows the user to visualize the "trade" in citations between technology categories for different time frames over different periods, and to consider either up- or down-citations, and either total citation trade, or just net. The number of arrows between two technology categories over the selected time period is selected with the "cutoff" value; the size of each category's disks shows the relative number of patents granted during that time period. Figure 3 is a nice illustration of the relationship between the two main categories of patents, those in the Chemical sphere, and those in the Computer sphere. Semiconductor Devices and Computer Peripherals seem to be the ambassadors between these two worlds.
For more information, see the following references.