Multidecadal dynamics project slow 21st-century economic growth and income convergence

Abstract

Future economic growth will affect societal well-being and the environment, but is uncertain. We describe a multidecadal pattern of gross domestic product (GDP) per capita growth rising, then declining, as regions become richer. An empirically fitted differential-equation model and an integrated assessment model—International Futures—accounting for this pattern both predict 21^st-century economic outlooks with slow growth and income convergence compared to the Shared Socioeconomic Pathways, similar to SSP4 (“Inequality”). For World Bank income groups, the differential-equation model could have produced, from 1980, consistent projections of 2100 GDP per capita, and more accurate predictions of 2010s growth rates than the International Monetary Fund’s short-term forecasts. Both forecasts were positively biased for the low-income group. SSP4 might therefore represent a best-case—not worst-case—scenario for 21st-century economic growth and income convergence. International Futures projects high poverty and population growth, and moderate energy demands and carbon dioxide emissions, within the Shared Socioeconomic Pathway range.

Socioeconomic scenarios with persistent inequality like that projected in SSP4 may represent best-case rather than worst-case scenarios for economic growth and income convergence in the 21st century, suggest differential-equation modelling and an integrated assessment model.