Comparing cities in developed and developing countries: Population, land area, building height and crowding

Historically, richer countries have had larger cities than poorer countries. Today, urban giants are no longer concentrated in rich countries. However, there are clear differences in physical city characteristics associated with country incomes. These differences are easily reconciled mathematically as population is the product of land area, structure space per unit land (i.e., heights), and population per unit interior space (i.e., crowding). This paper explores how these components have changed for the whole world and what remains of the association between income and city development using a combination of harmonized old and new databases. We document that cities in richer countries are large because they build "out" and build "up". Cities in poorer countries have become as large because they have crowded "in". Therefore, similar city sizes now hide stark differences in physical urban development. We also show how the Standard Urban Model can account for both similarities and differences in physical urban development across countries