Levels of urbanization in the world's countries: testing consistency of estimates based on national definitions

Estimates of urbanization levels for all countries, as published in the United Nations World Urbanization Prospects, are not comparable across countries because they are based on national definitions of urbanization, which vary greatly across countries. We construct alternative estimates of urbanization that are comparable across countries, to use these estimates to point out definitional problems or outlying countries with interesting urban characteristics. The alternative estimates are constructed using variables that are associated with urbanization, as well as a categorical variable that summarizes the urban definition used in the country. We find that among the 181 countries included in the analysis, 21 % have a restrictive definition, and 31 % a generous definition of urbanization. In 2000, the difference between the alternative estimate and the UN estimate was more than 10 % for 67 countries. An examination of six countries with surprisingly low or high reported levels of urbanization, as compared the alternative estimates, highlights issues with the plausibility of the official estimate. We conclude that comparison of urbanization estimates across countries should be treated with care, given the wide range of definitions used. To produce more informative estimates of urbanization, several countries would need to clarify or rethink their definition of urban.