Trajectories of top 3 cities per country (limited to population > 1M), 2013-2023. Click legend to highlight, hover over axis labels for details.
PM2.5 (air pollution). City-level PM2.5 concentrations are derived from the Atmospheric Composition Analysis Group (ACAG) global surface PM2.5 dataset (Washington University in St. Louis). For each city and year, we calculate the average PM2.5 concentration over the three most polluted months of that year to reflect peak (and most harmful) exposure conditions.
City GDP. City GDP is not widely measured or reported. We follow a standard modeling approach by rescaling national GDP data from World Development Indicators. National GDP is allocated to cities based on their population using a constant GDP–population elasticity of 1.1. This estimate is a global average from Bettencourt et al (2007), Bettencourt (2013), but probably overstates the income advantage of cities in richer countries and understates it in poorer ones. This is work in progress and will be updated as we develop more heterogeneous scaling estimates.