  Understanding the dynamics of patents and trademarks is a key aspect of
tracking innovative progress/egress. This paper empirically explores the
chronological Hurst exponent (CHE), an approach that calculates the Hurst
exponent over an increasing duration of time windows to quantify long-memory
dynamics, in the monthly numbers of United States patent and trademark
applications from 1977 to 2016. The CHE is found to increase in a clear
3-period S-curve pattern, achieving persistence (Period 3: H~1) from
non-persistence (Period 1: H~0.5). For patents, Period 2, the time-varying
period, occurred over a span of 10 years (1980-1990), while it was much sharper
(3 years) for trademarks (1977-1980). 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 persistency during Period 2.
Post-1990s exogenic variables led to the maintenance of the high degree and
consistency of the persistency metric. These findings suggest investigators
should consider latent persistency when using these data and the CHE may be an
important tool to investigate the impact of substantive exogenous variables on
growth dynamics.
