Hindered Growth

I will present a formalism to extract the exponential component from a growth process and describe the remainder with the optimal number of parameters. The method is demonstrated analyzing the time variation of population and GDP in the US and UK, two nations with continuous data coverage going back more than 200 years. For each of the four datasets we find a successful description, with the deviation of long-term growth from a pure exponential requiring no more than a single free parameter; there is no significant gain from adding more parameters. The remarkable persistence of simple, distinct long-term growth patterns for both GDP and population in both nations presents a major challenge to theory.