Patent indicator definitions

The work of Gao identifies a range of studies that have been conducted previously based on the principle of using either a single or multiple bibliometric indicators as a means of investigating technological development and performance \cite{Gao_2013}. Their review of these methods concluded that multiple patent indicators are required to avoid generating potentially unreliable results if just using a single indicator extracted from patent data. As such, the nearest neighbour classification process developed in Gao's study proposes the use of thirteen separate patent indicators. This current study has accordingly reproduced these metrics were possible, resulting in a total of ten patent indicators (i.e. producing time series for each technology with ten dimensions), as three of the previous list of indicators were specific to the Derwent Innovation Index \cite{2003} which was not used in this study due to the limited ability to bulk export the necessary results from this database. As such, Table \ref{table:bibliometric_indicators} summarises the bibliometric indicators extracted for each technology within this analysis.