A General Description of Growth Trends

Time series that display periodicity can be described with a Fourier expansion. In similar vein, recently developed formalism enables the description of growth patterns optimal number parameters Elitzur et al. 2020. The method has been applied to national GDP, population and COVID-19 pandemic; in all cases, deviations long-term from purely exponential required no more than two additional parameters, mostly only one. Here, I utilize new framework develop unified formulation for functions describe deceleration, wherein rate decreases time. result offers prospects general tool trend removal time-series analysis.