European Union – Statistics on Income and Living Conditions (EU-SILC)

European Union – Statistics on Income and Living Conditions (EU-SILC) is a household survey that was conducted by Czech Republic since 2005. A similar survey is launched in all 27 member countries of the European Union, as well as in Great Britain, Norway, Switzerland, Macedonia, Serbia, Turkey and Iceland. Methodology in all countries where the survey is conducted is harmonized and therefore the international comparison of social and living conditions of households is possible to make.

The EU-SILC is an instrument aiming at collecting timely and comparable both cross-sectional and longitudinal data on income, economic activity, poverty, material deprivation, social exclusion and living conditions. Nationally, the data from the survey could serve as a basis for social and family policy – both for its creating and checking its consequences in society.
 

Sampling, sampling units

The sampling unit is a dwelling. In the first wave all households and all the persons who have the dwelling as their usual place of residence are surveyed. During the waves 2–4 only those households that include a panel person (the one surveyed in the first wave) are surveyed.

The sample is obtained by applying a two-stage probability sampling scheme on each of the 14 administrative regions (NUTS3 regions) independently. The total number of dwellings selected in each region is proportional to the region's size. At the first sampling stage small geographical areas (CEUs – census enumeration units) are selected by probability sampling. These CEUs serve as a basis for the second-stage selection (a sample of 10 dwellings is drawn from each CEU).

In the survey a four-year rotational panel has been implemented, which means that the households are interviewed for four consecutive years. Every year approximately one fourth of the sample is newly introduced by replacing the households which were surveyed four times by new ones. To keep the sample size more or less the same, the number of new households is chosen to reflect the number of successfully interviewed households in the previous year.

The household definition is based on a declaration of the persons in a sampled dwelling that they live together and pool their income to cover expenditures catering for their needs.
 

Fieldwork

The survey is conducted face to face. Respondents' answers are entered into the questionnaires right in the household. A part of the selected households is still interviewed using paper questionnaires (PAPI), while the rest is interviewed using an electronic ones (CAPI).

The content of the survey is divided into four questionnaires with different units of reference. The survey consists of three stable parts (dwelling, household and personal questionnaires) and a part that alters from year to year (module):

Questionnaire A (dwelling questionnaire): contains a list of all persons with usual residence in the selected dwelling, their basic demographic characteristics, information on sharing of expenses to determine household units and relationship of each person to the main user of the dwelling and to the head of household.

Questionnaire B (household questionnaire): is filled in for each household; contains information on housing, consumer durables, financial situation of the household, consumption of the household's own production (i.e. small scale farming and similar activities), inter-household transfers paid and received, family social benefits, rental income, paid regular taxes on wealth (buildings and land) and childcare.

Questionnaire C (personal questionnaire): is filled in by each household member aged 16 years or over as of 31 December of the previous year; contains information on labour status and employment, personal income (from employment, private enterprise and social security schemes), participation in private pension plans, selected biographical information and health.

A regular, but varying part of the EU-SILC survey is called the module. Most of the times, the module elaborates one of the areas of the EU-SILC and gets detailed information on material deprivation, social participation, housing conditions, over-indebtedness or financial exclusion.

Table 1 A list of annual ad-hoc modules in EU-SILC survey, 2005–2023

Grossing up and weighting

When compared with data from other statistics and registers, selected characteristics of the EU-SILC sample show that a phenomenon typical of household surveys occurs – high level of non-response (in a rotational panel influenced by a prior response) biases the proportions in the final data file from which results are obtained. The deformation of demographic characteristics and social structure of the sample does not allow using of simple techniques of grossing up (post-stratification). To reach sufficient level of bias elimination, which is the necessary pre-condition for obtaining good estimates, it is necessary to use more sophisticated methods. In practice, the iteration method of weight calibration is utilized, which minimizes the difference between the known and the grossed up values of selected characteristics. Although it is a panel survey comprising data of four practically independent samples (waves 1–4), a simple calibration method is utilized which does not distinguish the waves but works with all households together. At the same time and according to the Eurostat’s recommendations the standard system of integrated weights is used in the survey, i.e. a single set of grossing-up coefficients that is subsequently used to produce results for both households and individuals. The target population of the survey are persons living in private households, therefore the data from demographic statistics are adjusted by subtracting institutionalized population (from social security administrative data and Ministry of Justice) and the persons living outside dwellings as based on the 2011 Census. As the sampling unit is the dwelling, all weight coefficients are calculated for dwellings and subsequently assigned to all persons and households in them (integrated weights).
 

Protection of individual data

At all stages of data processing and analyzing the anonymity of collected data is guaranteed. Any information that could lead to unequivocal identification of individuals or households is excluded. The data obtained are strictly protected in accordance with Act no. 89/1995 concerning the state statistics service and Act no. 101/2000 on individual data protection. All employees of the Czech Statistical Office working on the survey or processing the data are bounded by secrecy and cannot disclose any of the facts investigated in accordance with § 16 of Act no. 89/1995.
 

Publications

Exhaustive results of the EU-SILC survey are contained in a publication issued by the Czech Statistical Office under the rubric PEOPLE AND SOCIETY, subgroup Living conditions, Household Income and Expenditure. The publication entitled Household Income and Living Conditions is published annually and contains both methodological notes and tables on households and individuals, broken down by social group, income, number of children and working members, economic activity, region and other indicators. The publication is available at: https://www.czso.cz/csu/czso/prijmy-a-zivotni-podminky-domacnosti-x6dl59cm5z.
 

Process and aims of survey

Big disadvantage of sample surveys in general is non-response, which influences results significantly. Non-response is not random, it is characteristic for specific population groups. The highest non-response rate can be seen in the first wave in the EU-SILC. Total response rate is around 85 % in this survey.

Table 2 Response in EU-SILC survey, 2018–2023

The aim of the survey is to collect representative data on social and economic situation of the households in all participating countries. Complex evaluation of the situation of the Czech households, their level of poverty as well as the comparison with the situation in other countries would not be possible without data on income.