Eurostat collects demography and migration data from EU Members States' National Statistical Institutes (NSIs) and also from almost all non-EU Member States in Europe (including EFTA countries and Candidate countries to the EU). Data are collected at national and at regional level.

Countries supply demographic data to Eurostat on several occasions each year, which is then reflected in updates in the Eurostat database:

• The Demographic Balance data collection supplies to Eurostat the first demographic data of the year n-1 by end of June of year n: based on the total number of births, of deaths and of the net migration in year n-1 the total population on 1 January of year n is estimated. Data are available in the database table demo_gind at the beginning of July.
• The total usually resident population is collected by the end of August from EU Member States to fulfil specific purposes linked to EU legislation, in particular the weighting by Qualified Majority of the votes in the Council of the European Union. The definition of population is thus uniform in this case for all countries. This data is made available by the end of September in the database table demo_urespop.
• Countries are providing a forecast of the current year's population by the end of November. This data on monthly births, deaths, immigration and emigration occurred within the (ongoing) year is then published in the database tables demo_fmonth and demo_mmonth at the beginning of December.
• The main data collection of the year takes place in the last quarter of the year. Detailed data on different breakdowns of population, live births, deaths, immigration and emigration flows on the national as well as regional level are provided by the countries by the end of each year n for the year n-1 and are available in Eurostat database in March (year n+1), together with demographic indicators calculated by Eurostat based on this data.

Countries may send updates of the data they previously provided throughout the year. Accordingly, updates in the Eurostat database may occur outside of the four major updates outlined here.