Although the original data sources are population censuses and national population estimates published by each country’s national statistical offices, there are some differences in the subnational population numbers between the Subnational Population databases and official statistics. The reasons for such differences include the adjustments and applications that were made on the subnational population numbers from the official sources. For example, the original data was adjusted from national statistical offices to mid-year, because most censuses were conducted during the time other than mid-year, while our estimates are for mid-year. A calculation was then made to show the share of population in first level administrative unit, and then applied to the World Bank’s total population estimates to calculate the population in each first level administrative division. However, the World Bank’s total population estimates often differ from census’ total population. This is because they are often adjusted for under/over-numeration of the estimated subnational population figures, which also differ from the subnational population numbers from official sources.