The subnational population estimates are for first-level administrative divisions which refer to administrative divisions one level lower to the national level. The area coverage and names of these first administrative level division are different in different countries. For example: in countries like the United States, Brazil, and Mexico, they are called states and in countries like Ethiopia, Ghana, and Nepal they are named as regions, while in Bolivia and Benin they are called departments.

The first-level administrative division framework or classification available from the most recent census or national population estimates was used to estimate the subnational population for each country. However, for some countries, the subnational boundaries might change in the years following the latest subnational population data publication. In this scenario, the subnational population estimates might not represent the current subnational framework for some of the countries.