The Wage Structure Survey is a four-yearly statistical operation (using the results of the 2002 Survey), conducted within the framework of the European Union with common methodological and content criteria, for the purpose of obtaining comparable results regarding the structure and distribution of wages among its Member States. This survey researches the wage distribution, based on a large variety of variables, such as sex, occupation, branch of activity, years in the post, or the size of the company.
Beginning in the year 2004, and in those years when the four-yearly survey is not conducted, the Annual Wage Structure Survey obtains estimates of the gross annual earnings per worker, classified by type of working day, sex, economic activity and occupation. The information is obtained through the combined processing of the Social Security General Affiliation File (SS) and Model 190 statements: Annual Summary of Withholdings and Advance Payments on Personal Income Taxes by the State Tax Administration Agency (AEAT) and the Treasury of Comunidad Foral de Navarra, along with the occupation and work time variables provided by the survey attached to the INE Quarterly Labour Cost Survey.
Given that the Annual Survey is not compiled for those years in which the Four-yearly Survey is conducted, in order to enable the preparation of the time series, as of 2006 the information for these years is completed by incorporating the same tables that are compiled for the remaining years, but using the information from the Four-yearly Survey.