Evaluating inventive activity: the cost of nineteenth‐century UK patents and the fallibility of renewal data

It has long been recognized that counting patents offers a poor gauge of the extent and value of inventive activity, not least because the quality of patented inventions varies enormously. The Schankerman‐Pakes model provides a valuable alternative gauge that utilizes the data from renewal fees which are regularly paid to keep a patent in force. This article suggests, however, that the model's application to nineteenth‐century UK patents may underestimate the value of Victorian inventive activity because many patentees lacked the financial resources to implement the rational choice that the model assumes. Focusing on steam‐engineering patents, it explores further problems with renewal data and the increasing rate of lapsed applications.