Population, total - Middle income, Lower middle income, Upper middle income, High income
World Population Prospects, United Nations ( UN ), uri: population.un.org/wpp, publisher: UN Population Division;
Statistical databases and publications from national statistical offices, National Statistical Offices, uri: unstats.un.org/home/nso_sites, publisher: National Statistical Offices;
Eurostat: Demographic Statistics, Eurostat ( ESTAT ), uri: ec.europa.eu/eurostat/data/database?node_code=earn_ses_monthly, publisher: Eurostat;
Population and Vital Statistics Report ( various years ), United Nations ( UN ), uri: unstats.un.org, publisher: UN Statistics Division
