Patents are considered to be major sources of technological and competitive information. Patent documents contain various types of information like applicant's & inventor's details, International Patent Class (IPC); detailed technological information, citations to prior art, claims, geographical location etc. The patent data is increasingly available on internet and have excessively potential for technologists in the field of technical change and innovation. Various methods have already been reported to analyze the patent data. Currently, business professionals, scientists and researchers are using patent information to analyze patenting activity in a geographical area, technology or company to determine the direction of technological transformation, or determine the relative technological scenario of an organization in a marketplace.

Generally technologists are using patents and their subsequent citations to measure the inventive output of any organizations. They have also used citation intensity to measure the importance or impact of the inventions.

Patent Citation:

Patent citations are the references defining technology already known within either patents or other scientific literature on which the present patent shaped or which it uses. They are very much similar to the citations in any research paper. In the patent system, when a new patent is filed, the inventor references the known prior art, and explains how the new invention represents an advance over this known prior art. In some cases, the new invention represents a makeable improvement over existing technology, while in other cases the invention may be a completely new use of a scientific discovery. Citations have been accepted as a noisy but useful metric for measuring knowledge spillovers and for studying innovation in general. Analysis of patent citations can be used to get an idea of the technology growth and also to measure the quality of patents.

There are basically two kinds of citations viz; backward citation and forward citation. The backward citation is a reference given in a patent on the prior art while the forward citation is a reference to the given patent by another patent.

Citation analysis is based on the principle that the number and nature of forward and backward citations are indicators of patent value; specifically, that greater numbers of forward citations indicate greater value. Backward citations of the patents can be studied to get an idea about the origin of technology and its flow over time. There is an explicit relationship between the importance of a patent and its forward citation.

Sometimes the patent citations are self-citations in the sense that a patent receives citations by patents applied for either by the same inventor who developed the original patent or by the same company that applied for the original patent.

In most of the cases the citations that appear in patents are to patents that were assigned to the same assignee as the citing patent. These citations are referred as "self citations." One possibility is that they appear simply because patents of the same company are well-known to the parties, or because of an inventor's desire to acknowledge colleagues. If so, then self-citations ought to be economically less significant than other citations. On the other hand, companies citing their own patents could be a consequence of the cumulative nature of innovation and the "increasing returns" property of knowledge accumulation, particularly within a narrow field or technology trajectory. Self-citations could suggest that the company has a strong competitive position in that particular technology. This will imply that the company has lower costs because there is less need to acquire technology from others. The presence of self-citations may thus be indicative of successful appropriation by the company of cumulative impacts, while citations by others might indicate cumulative impacts that are spilling over to other companies. If so, then the private value of self-citations should be greater than that of other citations.


Patent citation analysis is an important technique which can be used to study the evaluation of science and technology. The basic principle behind its use is that papers or patents cited as prior art by many later patents tends to contain important ideas upon which numerous inventions have been built. This does not mean that every important document is highly cited, or that every highly cited document is important. However, numerous validation studies have revealed the existence of a strong positive relationship between citations and technological importance.

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