Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
We develop 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 Gross Domestic Product (GDP) and population 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. We find persistent long-term growth patterns, consistent with Jones (1995) and showing directly from the data that population and GDP growth in different countries may follow different trajectories, illuminating their intrinsic differences.