Figure 3
A heat map of the United States showing the gravity map of population in 2021. The map uses a color scale ranging from green to red, with green indicating lower population density and red indicating higher population density. The highest population densities are concentrated in the northeastern and southeastern regions of the United States. A second heat map of the United States showing the gravity map of GDP in 2021. This map also uses a color scale ranging from green to red, with green indicating lower GDP values and red indicating higher GDP values. The highest GDP values are concentrated in similar regions as the population density, particularly in the northeastern and southeastern United States.Gravity map of the US; population in 2021 (at the top) and GDP in 2021 (at the bottom). Both figures are based on absolute values and feature the 75th percentile as maximum value. Source: personal elaboration