The Flash Eurobarometer, in accordance with the standard series, usually provide two types of weighting. For post-stratification weighting (also refered to as "redressment" or "unit non-response weighting") a comparison between the sample and the universe was carried out country by country. Starting with Flash Eurobarometer 183 the relevant (active) variables which are introduced in the iteration (raking) procedure are stated as being for all countries: age by sex groupings, activity (active worker, retired, other non-active), and regions NUTS II. The universe description is usually gathered from local statistical offices.
In the case of special target group surveys, corresponding relevant variables are used in national raking precedures (e.g. activity and company size for samples of enterprises).
The population size weighting corrects for the fact that most countries have almost identical sample sizes, no matter how large or small their populations are. They ensure that each country is represented in proportion to its population size when the group of all countries is the object of study (i.e. country group averages). The population size weights usually include the post-stratification weighting factors.
If surveys are conducted in mixed-mode, face-to-face and webCATI (see sampling and fieldwork information), additional dual-frame weighting is introduced dealing with telephone owners for the countries concerned. This TELEPHONE ACCESS WEIGHT is based on information on the fix-phone lines and directory listed fix phone numbers in the household (selection probability depending on number telephone lines).
Official EC publications (reports) are usually based on weighted data.
The COUNTRY FACTOR is supposed to be applied for descriptive analysis whenever individual countries are analysed separately. This "sample internal" weighting factor reproduces the real number of cases for each country. There is not necessarily such a weight for the special target group surveys.
Population size weights (including post-stratification)
The EU FACTOR is mandatory when analysing the group of all member countries, or specific historical subgroups (e.g. the new member countries as of 2004) as a whole. Special target group surveys may include this weight without post-stratification factors.
For UNIVARIATE (descriptive) analysis the application of the Eurobarometer POST-STRATIFICATION WEIGHTS is recommended, the application of the POPULATION SIZE WEIGHTS mandatory. Official Eurobarometer reports are based on weighted data.
Recommended for reading
Häder, Sabine; Gabler, Siegfried (1997): Deviations from the Population and Optimal Weights, in: Saris, Willem E.; Kaase, Mas (eds.): ZUMA Nachrichten Spezial. Band 2, Mannheim.
Arzheimer, Kai (2009): Gewichtungsvariation. In: Schoen, Harald; Rattinger, Hans; Gabriel, Oscar (Hrsg.): Vom Interview zur Analyse. Baden-Baden. S. 361-388.
Gabler, Siegfried; Ganninger, Matthias (2010): Gewichtung. In: Wolf, Christof; Best, Henning (Hrsg.): Handbuch der sozialwissenschaftlichen Datenanalyse: VS Verlag für Sozialwissenschaften, S. 143-164.