Why does the United Nations use each country’s definition of urban areas?

The United Nations relies on individual countries' definitions of urban areas because there is no universal, standardized threshold for what constitutes an urban environment versus a rural one. As noted in social science, the criteria for population numbers and densities that qualify an area as urban vary significantly based on each nation's specific census categories and administrative guidelines.1

Because urban areas are defined by complex factors—including population density, economic activities like industry and commerce, and distinct social structures—different countries tailor their definitions to reflect their unique demographic and geographic realities. Consequently, the United Nations adopts these national definitions to maintain consistency with how each sovereign state tracks its own demographic data and government planning.1