A hybrid model for the patent citation network structure

Abstract

Percolation theory on the patent citation network is studied and the percolation threshold points are identified. The results show that there is a significant change of the threshold throughout our dataset years, implying changes in the formation process of the patent citation network. There is a first shift at around 2001, and a very delayed transition point after 2008. Giant component formation in such networks is an indication of the existence of inter-disciplinary patents. In order to explain the changes observed, a hybrid model for creating networks is suggested here. The model is based on a combination of random networks and preferential attachment. It is also compared with results from the well-known configuration model. The hybrid model fits better the data of the patent citation network, rather than a single scale-free or a single Erdős–Rényi network, and explains the increase in preferential attachment in later years. Both the degree distribution and the results of the analysis through percolation theory agree well with real data. This enables the formation of a plausible explanation for the structural changes of the patent citation network’s evolution.