- Vernon Henderson: data on metropolitan areas (henceforth, MAs) in different countries during the 1960–2000 period.
- Thomas Brinkhoff: information on the populations of various administratively defined cities (henceforth, cities) in 79 countries during the 1970–2000 period.
- Jan Lahmeyer, the most comprehensive dataset, includes the size of the largest cities for all countries up to the year 2000 and going as far back as 1790 in some cases.
Minhas and Radford (2016) use The World Alamanac, which "lists the major cities in a country by population... Typically, the Almanacs list at least three major cities, including the capital, for each country and year from 1989 to 2008. Because the Almanacs are not perfectly consistent from year to year, we opted to code cities with a five-year rolling window. That is, cities listed in the 1995 Almanac are also included in our data set for years 1993 to 1997. In doing so, we hope to minimize the effect of coding inconsistencies on the part of The World Almanac."