The Annual Wage Structure Survey (AWSS) is an annual statistical operation that has arisen out of the need for annual wage information classified by sex. It is the source of information for the compilation of the "Gender Pay Gap" Structural Indicator requested each year by Eurostat.
The legal basis for the preparation of this statistical operation is the same basis regulating the Wage Structure Survey that is conducted every four years, allowing the integration of the results for both statistics, though the number of variables studied in the annual operation is smaller.
The objective of the Annual Wage Structure Survey is to ascertain the wage distribution, based on individual and collective characteristics.
It provides estimates of the gross annual earnings per worker, classified by different characteristics, such as sex, occupation, economic activity, age, etc.
The survey enables offering results, both on a national level and by Autonomous Community.
The survey uses the National Classification of Economic Activities, CNAE-2009, and the National Classification of Occupations NCO-11.
The sectoral coverage encompasses from Section B to Section S of CNAE-2009.
The occupation coverage includes those occupations included in Large Groups 1 to 0 from NCO-11.
The survey uses two types of statistical unit:
1. The Contribution Accounts included in the General Register of Social Security Contribution Accounts.
The Social Security Contribution Account is a concept traditionally used in wage and labour cost surveys, both by the INE and by other bodies with jurisdiction in this area.
2. The workers employed by others associated with the Contribution Accounts.
The target contribution accounts of study are those whose economic activity belongs to Sections B to S of CNAE-2009, and which are in the General Register of Social Security Contribution Accounts at 30 September of the reference year.
The workers included in the survey are those who work for others in target contribution accounts of study of the survey, and who have been registered in Social Social more than two months of the year, with one of those months being October. The inclusion of this month is due to the advantage of being considered "normal" in all EU countries, in the sense that it is scarcely affected by seasonal variations or by payments with a due date longer than a month, such as the Christmas payments.
It excludes all chairpersons, members of administrative boards, and in general, all personnel whose remuneration is not mainly in the form of wages, but rather commissions or benefits.
The geographical scope encompasses the entire national territory, with results broken down by Autonomous Community.
The survey is carried out annually. Results thereof are available as of the year 2004. The data referring to years 2006, 2010 and 2014 has been obtained from the Wage Structure Survey, which is conducted every four years, rather than the Annual Wage Structure Survey.
The Annual Wage Structure Survey has been affected by numerous methodological changes, due to the implementation of new classifications in both economic activity and occupation. As a result, the last homogeneous series began in 2008, using the National Classification of Economic Activities, CNAE-2009, and the National Classification of Occupations, NCO-11.
The data refers to the target calendar year of the survey.
Data referred to the period: Anual A: 2017
The compilation and dissemination of the data are governed by the Statistical Law No. 12/1989 "Public Statistical Function" of May 9, 1989, and Law No. 4/1990 of June 29 on “National Budget of State for the year 1990" amended by Law No. 13/1996 "Fiscal, administrative and social measures" of December 30, 1996, makes compulsory all statistics included in the National Statistics Plan. The National Statistical Plan 2009-2012 was approved by the Royal Decree 1663/2008. It contains the statistics that must be developed in the four year period by the State General Administration's services or any other entity dependent on it. All statistics included in the National Statistics Plan are statistics for state purposes and are obligatory. The National Statistics Plan 2017-2020, approved by Royal Decree 410/2016, of 31 October, is the Plan currently implemented. This statistical operation has governmental purposes, and it is included in the National Statistics Plan 2017-2020. (Statistics of the State Administration).
Council Regulation no. 530/1999, of 9 March 1999, relating to structural statistics on wage earnings and wage costs.
Commission Regulation no. 1738/2005, of 21 October 2005, amending Regulation (EC) no. 1916/2000, referring to the definition and transfer of information regarding the structure of wage earnings.
The Spanish version of the European Union regulations affecting this statistical operation is available at:
In order to conduct this survey, administrative register data from the General Social Security Treasury, the State Tax Administration Agency and the Tax Agencies of Navarra, Bizkaia and Gipuzkoa is used.
The tables published do not show data in those cells whose estimation is supported by fewer than 100 sample observations.
The survey is disseminated annually.
It must be noted that the data referring to the years 2006, 2010 and 2014 is from the Wage Structure Survey, and it is totally comparable with that obtained in the remaining years.
Users may access the data via the INE website. Specifically, the data appears in the following links:
- Press release: this contains a summary of the results obtained in the reference year.
- Results of detailed: this contains the series compiled in CNAE-2009 and NCO-11.
- Related links in INEbase: this is where the series compiled in classifications used in previous years are presented. There are two sections:
1. Detailed CNAE-2009/NCO-94 results: 2008-2009 Series.
2. Detailed CNAE-93/NCO-94 results: 2004-2007 Series.
They include information from free online publications of the AWSS, such as: "Spain in Figures," "Statistical Yearbook of Spain," etc.
INEbase is the system the INE uses to store statistical information on the Internet. It contains all the information the INE produces in electronic formats. The primary organisation of the information follows the theme-based classification of the Inventory of Statistical Operations of the State General Administration . The basic unit of INEbase is the statistical operation, defined as the set of activities that lead to obtaining statistical results on a determined sector or subject based on the individually collected data. Also included in the scope of this definition are synthesis preparation.
The tables and time series may be accessed in INEbase, within the Society/Labour market section, and through the following link:
No anonymised microdata file is provided for this statistical operation.
There is the option of requesting tailor-made information from the INE Customer Service Area. Limitations to confidentiality or precision are borne in mind at the time of processing said requests.
The link to the INE Customer Service Area is as follows:
For a detailed description of the methods and concepts used, as well as of other documents related to the Annual Wage Structure Survey, please see the following webpage:
Fields 10.6 to 17 of this document may be considered the quality report intended for users for this operation.
Quality assurance framework for the INE statistics is based on the ESSCoP, the European Statistics Code of Practice made by EUROSTAT. The ESSCoP is made up of 16 principles, gathered in three areas: Institutional Environment, Processes and Products. Each principle is associated with some indicators which make possible to measure it. In order to evaluate quality, EUROSTAT provides different tools: the indicators mentioned above, Self-assessment based on the DESAP model, peer review, user satisfaction surveys and other proceedings for evaluation.
The compilation process of the statistics has established controls for detecting and correcting errors, for the purpose of guaranteeing the quality thereof from the beginning of the process onward. The collection, recording and filtering processes of the information are fundamental stages in the development of any statistical research.
Prior to processing the information, a comprehensive control of the data provided by the respondent units is performed, in order to ensure the validity thereof.
The data received passes through a dual control:
- A first filtering, simultaneous to the recording, which has the objective of detecting incomplete and erroneous questionnaires, as well as guaranteeing the coherence of the data recorded.
- A second control, in order to avoid inconsistency between related variables obtained from the surveys and from the administrative registers, which is combined with a macrofiltering based on the elevated data obtained.
Once all of the information is validated, macrofiltering analyses are performed, using the results obtained and their comparison with previous periods.
The Annual Wage Structure Survey is a high-quality product. Its sample size allows for offering indicators up to a regional level, within reasonable sampling errors, and provides a particularly valuable measurement of wage evolution.
Regarding the limitations of the survey, it is important to point out those that are inherent to statistical operations by sampling, such as non-response and the aforementioned sampling errors or variation coefficients of the estimates. In both cases, they remain within reasonable limits.
Survey users include:
- Ministries and other public bodies.
- Territorial administrations (Autonomous Communities, municipal councils, etc.).
- Businesses and non-profit institutions, trade unions and employers' organisations.
- Researchers and universities.
Each one of these users has different needs, according to the purpose and use they will make of the information they require.
The INE has carried out general user satisfaction surveys in 2007, 2010, 2013 and 2016 and it plans to continue doing so every three years. The purpose of these surveys is to find out what users think about the quality of the information of the INE statistics and the extent to which their needs of information are covered. In addition, additional surveys are carried out in order to acknowledge better other fields such as dissemination of the information, quality of some publications...
On the INE website, in its section Methods and Projects / Quality and Code of Practice / INE quality management / User surveys are available surveys conducted to date.(Click next link)
In the user satisfaction survey conducted in 2016, which can be consulted on the website of INE in the category of Quality -> Quality Management -> System evaluation and quality monitoring -> User surveys , you can see the evaluation of "labor market" group in which it is framed this statistical operation . This can give us indications of user opinions of this statistical operation.
In general, users are satisfied. However, they believe that the survey should have a larger sample size, in order to offer a more detailed breakdown of some variables (in particular, of the geographical breakdown, of economic activities and of cost components).
The Annual Wage Structure Survey is a fundamental source of information for the preparation of the "Gender Pay Gap" Structural indicator, and therefore, it is subject to regulation by said indicator. Therefore, the rate of compulsory information provided is R1=100%.
The sample design tries to minimise the sampling errors, and the different survey processes are aimed at eliminating, or reducing as much as possible, the errors thereof, both in the collection phase (response rate and filtering control) and in the subsequent editing and imputation phases.
The calculation of variation coefficients of the main variables is carried out each time the survey is compiled, and they are disseminated in its publication and in subsequent quality reports.The variation coefficients of the annual earnings by gender are: "Annual earnings" A1=0.5%; "Annual earnings, male" A1=0.7%;"Annual earnings, female" A1=0.8%.
For greater detail, please see section 5 of the survey publication:
Non-sampling errors are controlled throughout the entire statistical process.
The Annual Wage Structure Survey is collected in parallel with the Quarterly Labour Cost Survey, as the former is a subsample of the latter. Therefore, for further information regarding non-sampling errors, it suffices to see this section in the QLCS metadata: https://www.ine.es/dynt3/metadatos/en/RespuestaDatos.htm?oe=30187
Item non respose is not allowed. The average non-response rate for the reference period of 2017 data has been A4=3.8%.
In cases of non-response, the imputation of the occupation is performed, using other available variables on the workers. A7=3,6%
The data for the statistics is published 17 months following the end of the information reference period. TP2=17 months
The dissemination of the data is carried out in accordance with the structural statistics availability calendar that the INE compiles and publishes for each year.
The availability of a methodology, a design and a common process for the collection, filtering, editing and elevation for the entire geographical scope, guarantees the comparability of the results among the different Autonomous Communities.
The international comparability of the data provided by this statistical operation is guaranteed, as it is carried out following the existing community regulations.
The results, broken down by CNAE-2009 section and sector, are comparable over time as of the year 2008, and therefore, there are CC2=10 comparable elements.
The results, broken down by CNO-2011 main occupation group, are comparable over time as of the year 2008, and therefore, there are CC2=10 comparable elements.
The use of the same national classification of economic activities allows for the possibility of contrasting the information with other statistics on common variables, such as the Living Conditions Survey.
The estimates of the Annual Wage Structure Survey have complete internal coherence, since they are based on the same microdata set and are calculated using the same estimation methods. The arithmetic and accounting identities in the production of data sets are observed.
The use of administrative registers in this statistical operation leads to a considerable reduction in the response burden.
The fact that the Annual Wage Structure Survey is collected together with the Quarterly Labour Cost Survey leads to the fact that all of the actions performed in order to avoid an excessive response burden in this survey affect the Annual Wage Structure Survey.
The estimation of the budgetary credit necessary to finance these statistics, as foreseen in the 2019 Annual Programme, comes to a total of 65,81 thousand euros.
The INE of Spain has a policy which regulates the basic aspects of statistical data revision, seeking to ensure process transparency and product quality. This policy is laid out in the document approved by the INE board of directors on 13 March of 2015, which is available on the INE website, in the section "Methods and projects/Quality and Code of Practice/INE’s Quality management/INE’s Revision policy" (link).
This general policy sets the criteria that the different type of revisions should follow: routine revision- it is the case of statistics whose production process includes regular revisions-; more extensive revision- when methodological or basic reference source changes take place-; and exceptional revision- for instance, when an error appears in a published statistic-.
There is no data revision.
The data is published when it is final. It is not subject to revision.
The Annual Wage Structure is a combination of the use of administrative registers and the conduction of a direct survey.
The random sampling process of units corresponds to a stratified two-stage sampling, where the first-stage units are the Social Security contribution accounts, while the second-stage units are the workers.
The sample selected in the first stage is the same as that selected in the Quarterly Labour Cost Survey. A stratified random sampling with optimal allocation is used, in which the sample units are the contribution accounts. The stratification criterion is performed, based on three variables: the Autonomous Community (17 in total, considering Ceuta and Melilla together with Andalucía), the economic activity (CNAE-2009 division, 82 divisions in total) and the size of the units (8 strata or size groups).
The size of the units is defined by the number of workers grouped therein. The following groups are considered for the stratification: 1-4 workers; 5-9 workers; 10-19 workers; 20-49 workers; 50-99 workers; 100-199 workers; 200-499 workers; 500 workers or more.
The strata with 500 workers or more are studied comprehensively. Within each stratum, the units are selected via systematic random-start sampling.
The list of units selected in the first stage is submitted again to the General Social Security Treasury, and the list of workers who were registered during the reference year is obtained.
This list is used to select the workers, where the number of workers to be selected in each centre depends on the total wage earners in said centre who have been registered in Social Security for at least two months, one of them being October. The selection is performed via systematic sampling, within each contribution account, with the lists of workers being previously ordered, first by Social Security contribution account, and with each contribution group, by sex, in such a way that the representativeness of the sample is ensured.
The information relating to the occupation of the workers is obtained from the questionnaires, and in the case of workers from País Vasco, the information relating to the annual earnings of said workers is also obtained. The rest of the information on earnings is obtained through requests made of the State Tax Administration Agency and the Tax Agency of Navarra.
The sample comprises some 28,000 contribution accounts, and approximately 220,000 workers.
For further information, please see the website:
The data collection is annual, regardless of whether it is that carried out by direct survey or that which comes from the administrative registers.
The respondent contribution accounts answer the survey questionnaire either online, by ordinary post (questionnaires filled out on paper); or by e-mail.
The first stage of data validation is carried out in the data collection centres, in which errors and inconsistencies in the information received from the respondent units is detected.
Subsequently, a second validation stage is performed by adding the data obtained from the respondents to that obtained from administrative registers.
In cases of non-response, the imputation of the occupation is performed, using other available variables on the workers.
In order to obtain the elevated results, it uses separated ratio estimators, using the number of workers in the Social Security Contribution Account Directory as an auxiliary variable.
No seasonal adjustments are carried out.