Before revision:  Based on these data, it is hypothesized that the rapid augmentation in exogenous variables (such as increasing R&D expenditure or specific policy initiatives (viz. , Bayh Dole, Stevenson-Wydler) are the key impetuses behind the increase of persistencyduring Period 2. Post-1990s exogenic variables led to the maintenance of the high degree and consistency of the persistency metric.
After revision:  Based on these data, it is hypothesized that the rapid augmentation in exogenous variables (such as increasing R&D expenditure or specific policy initiatives (viz. , Bayh Dole, Stevenson-Wydler) are the key impetuses behind persistency, latent in PTA. The post-1990s exogenic factors seem to be simply maintaining the high degree and consistency of the persistency metric.