A patent evaluation method analyzes key words in the claims and how many patents use those words, to measure the impact of a given patent. For a group of patents in a particular field (e.g., as defined by a patent classification code), the key words can be indexed against the patents having claims in which those key words appear, and in particular with respect to that patent having the earliest reference date (e.g., a publication date such as the date on which the patent issued or any corresponding patent application was published). Output may be presented in the form of a table, which aids in quickly understanding a patent's value compared to other patents in its group. Various visualization and user interaction tools may be employed.