Methodology 

The Active population survey (EPA) is the main source of statistical information on the labour market. Its main objective is to find out about the population's relation with economic activity. The EPA collects information about the type of occupation of the employed population and unemployed that have worked before. These variables are codified in accordance with the official statistical classifications corresponding to each period.

The National classification of occupations 2011 (CNO-2011) is a statistical instrument for classifying types of occupation. It came into force on January 1, 2011, and is to be applied by obligation to official Spanish statistics. To adapt to the new National classification of occupations 2011 (CNO-2011), the EPA started the first quarter of 2010 using a double codification of the employment variables used in the applicable classification of the time (CCO-94) and the new Classification (CNO-2011). One of the objectives of this procedure is the obtainment of retrospective series for the most important population magnitudes, to enable comparison of results from a period prior to the moment that the new classification came into force.

The retrospective series for the employed population in accordance with the CNO-2011 for the 2000–2009 period were calculated on the basis of the double coded system used between the CCO-94 and the CNO-2011. The coefficients used in this system were determined on the basis of the disaggregation into two digits in the two classifications of the annual average for the employed population in the year 2010. The estimations for large employment groups were made by aggregating the corresponding codes into two digits.

The results for the employed population for the 2000–2009 period with the CNO-2011 are published on the level of large employment groups.