Euro-SDMX Metadata Structure (ESMS)
National Statistical Institute
|Contact organisation unit|
Statistics on Living Conditions Department,
Demographic and Social Statistics Directorate
Desislava Dimitrova, PhD
|Contact person function|
head of department
|Contact mail address|
2 P.Volov street, 1038 Sofia
|Contact email address|
|Contact phone number|
+359 2 9857 183
|Contact fax number|
|Metadata last certified||05 August 2019|
|Metadata last posted||05 August 2019|
|Metadata last update||05 August 2019|
Survey on income and living conditions (SILC) is a tool for providing timely and comparable data on income distribution, level and structure of poverty and social exclusion. The survey is carried out in a European methodology and provides information about the current state (cross-sectional data) and longitudinal (longitudinal data) changes in income level and structure of poverty and social exclusion.
EU-SILC provides four basic files containing target variables based on common concepts and definitions.
Annual data for the countries contain the following components:
• Household register (D-file);
• Personal register (R-file)
• Household data (Н-file)
• Personal data of people aged 16 and more (Р-file)
Each year additional data on the household and household members on specific topics is collected, the so-called ad-hoc modules.
The indicators on poverty and social inclusion are calculated on the basis of the survey "Statistics on income and living conditions" and a common methodology for data collection, target variables obtaining and calculating of common indicators, approved by Eurostat. The poverty rate is the share of households that are below the poverty line which is defined as 60% of the median equivalised disposable income.
The following social fields are included in the survey methodology:
|Statistical concepts and definitions|
Total household income:
Two main concepts for total household income are applied:
Total household gross income (HY010) is computed as the sum for all household members of gross personal income components:
Total disposable household income (HY020) can be computed as total household gross income (HY010) is reduced to:
Household is two or more persons, living in one dwelling or part of dwelling, sharing common budget and eating together.
Household is a person, living in one dwelling, room or part of it to a dwelling, has a separate budget for the cost of meals and expenses to satisfy other needs.
For the calculation of indicators of poverty and social inclusion using the total disposable household income is "equalised". Due to the different composition and number of persons in the household equivalent scales apply. Use the modified OECD scale, which gives a weight of 1.0 to the first person aged 14 or more, a weight of 0.5 to other persons aged 14 or more and a weight of 0.3 to persons aged 0-13. The weights are given to each member of the household and summed to obtain an equivalent household size. Total disposable net income for each household is divided by its equivalent size and form the total disposable net income per equivalent unit.
Units of observation are households and household members.
The EU-SILC target population consists of all private households and their current members residing in the country. Persons living in collective households and in institutions are generally excluded from the target population.
Entire territory of Republic of Bulgaria
2006 - 2018
|Unit of measure|
BGN, euro, percent (%), number of persons
EU-SILC uses the following reference periods for the different variables included in the survey:
The income reference period is the previous calendar year;
|Legal acts and other agreements|
· Regulation (EC) No 1177/2003 concerning Community statistics on income and living conditions (EU-SILC);
· Regulation (EC) No 1553/2005 amending Regulation (EC) No 1177/2003;
· Regulation (EC) No 1980/2003 implementing Regulation (EC) No 1177/2003 of the European Parliament and of the Council concerning Community statistics on income and living conditions (EU-SILC) as regards definitions and updated definitions;
· Regulation (EC) No 1981/2003 implementing Regulation (EC) No 1177/2003 of the European Parliament and of the Council concerning Community statistics on income and living conditions (EU-SILC) as regards the fieldwork aspects and the imputation procedures;
· Regulation (EC) No 1982/2003 of 21 October 2003 implementing Regulation (EC) No 1177/2003 of the European Parliament and of the Council concerning Community statistics on income and living conditions (EU-SILC) as regards the sampling and tracing rules;
· Regulation (EC) No 1983/2003 of 7 November 2003 implementing Regulation (EC) No 1177/2003 of the European Parliament and of the Council concerning Community statistics on income and living conditions (EU-SILC) as regards the list of target primary variables;
- Regulation (EC) No 2256/2015 of the Commission of 4 Dec 2015 amending Regulation (EC) No 1983/2003 implementing Regulation (EC) No 1177/2003 of the European Parliament and the Council concerning Community statistics on income and living conditions (EU-SILC) as regards the list of target primary variables;
· Regulation (EC) No 28/2004 of 5 January 2004 implementing Regulation (EC) No 1177/2003 of the European Parliament and of the Council concerning Community statistics on income and living conditions (EU-SILC) as regards the detailed content of intermediate and final quality reports.
|Confidentiality - policy|
|Confidentiality - data treatment|
According Art. 25 of the Statistics Act individual data are not published (they are suppressed). Dissemination of individual data is possible only according to Art. 26 of the Statistics Act.
Statistical information is published according to the Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute.
|Release calendar access|
The Calendar is available on the NSI's website: http://www.nsi.bg/en/node/480
The data for Income and living conditions (EU-SILC) are published on NSI website, section Social Inclusion and Living Conditions in accordance with the Law on Statistics (Chapter 5) and the European Statistics Code of Practice, respecting professional independence and in an objective, professional and transparent manner in which all users are treated equitably.
|Frequency of dissemination|
|Accessibility and clarity|
Poverty and Social Inclusion Indicators.
Detailed results are available to all users of the NSI website under the heading Social Inclusion and Living Conditions - Poverty and Social Inclusion Indicators: http://www.nsi.bg/en/node/8292
Anonymised individual data can be made available for scientific research purposes, and at the individual request of the Rules for the provision of anonymised individual data for scientific and research purposes.
Information service on request, according to the Rules for the dissemination of statistical products and services to NSI.
|Documentation on methodology|
Detailed information about the list of social inclusion indicators, definitions and algorithm for their calculation can be found on the following site:
National Quality Report according to Regulation (EC) 28/2004.
The Survey on Income and Living Conditions (SILC) is an annual survey implemented in the framework of Regulation (EC) No 1177/2003, which defines Scope, Definitions, Time coverage, Characteristics of the data, Sample size, Publication and Access to data.
Data are accompanied with quality reports analysing the accuracy, coherence and comparability of the data.
BG-SILC the main users are:
SILC covers only people living in private households (all persons aged 16 and over within the household are eligible for the operation), i.e. persons living in collective households and in institutions are generally excluded from the target population.
|Accuracy and reliability|
As with any other statistical survey, SILC may be burdened with errors due to sampling and other relating to the inability to be interviewed some of the units in the sample, as well as the errors taking place at the stage of data recording, data processing, etc.
Regulation 1177/2003 defines the minimum effective sample sizes to be achieved to compensate for all kinds of non-response. The allocation of the effective sample size is done according to the size of the country and ensuring minimum precision criteria for the key indicator at national level (absolute precision of the at-risk-of-poverty rate of 1%).
Computations of standard errors were carried out using SAS programs for the SILC Quality Reports and Complex Sample analysis in SPSS ver.20.
Non-sampling errors are basically of 4 types:
|Timeliness and punctuality|
SILC cross-sectional and longitudinal data are available in the form of tables 12 months after the end of the data collection period.
|Coherence and comparability|
According to the Regulation (EC) No 1177/2003 of the European Parliament and of the Council concerning EU-SILC: "Comparability of data between Member States shall be a fundamental objective and shall be pursued through the development of methodological studies from the outset of EU-SILC data collection, carried out in close collaboration between the Member States and Eurostat".
Although the best way for keeping the comparability of data is to apply the same methods and definitions of variables, small departures of the definitions given by Eurostat are allowed in EU-SILC. In this way, the mentioned Regulation in its article 16th says: "Small departures from common definitions, such as those relating to private household definition and income reference period, shall be allowed, provided they affect comparability only marginally. The impact of comparability shall be reported in the quality reports."
The coherence of two or more statistical outputs refers to the degree to which the statistical processes, by which they were generated, used the same concepts and harmonised methods. A comparison with external sources for all income target variables and the number of persons who receive income from each ‘income component’ will be provided, where the Member States concerned consider such external data to be sufficiently reliable.
|Comparability - geographical|
Comparability across EU Member States is considered high due to use of harmonised concepts, variables, definitions and classifications.
|Comparability - over time|
|Coherence - cross domain|
The cross-sectional data for the EU-SILC2018 were compared to the Labor force survey 2018 and HBS 2018.
When comparing SILC and HBS we must take into account the discrepancies. The differences are to great extent brought about by the methodological diversity. Here are the main methodological differences:
|Coherence - internal|
|Cost and burden|
The total length of interviewing household in average below 67 minutes.
|Data revision - policy|
|Data revision - practice|
The sample for EU-SILC 2018 are selected from the sampling frame based on the Population Census 2011. The data base includes all private households and their current members residing in the country. Persons living in collective households and in institutions are excluded from the target population. Student’s and worker’s hostels are excluded at the first stage of selection of PSU, because student’s and worker’s households rarely stay on the same addresses and are difficult to trace.
The frame is regularly updated according to the administrative changes made.
Household data within the selected PSUs are updated according to the Information System “Demography” data (ISD).
The longitudinal component consists of the sub-samples R1, R3, R4, R5 and R6.
All personal/household income variables were collected by interview.
In some cases, where the information on income component is unavailable a register to obtain missing value information is used. The National Social Security Institute keeps a register of all persons for whom employers pay social insurance contributions and of all self-insured persons. This register contains some data on personal income but it is generated by a labour activity of the persons and moreover, this is only the income on which the person was insured. From Social Assistance Agency obtained on income from social benefits
Two stage sampling on a territorial principle is implemented as follows:
- on the first stage - the census enumeration units (PSU) are selected;
- on the second stage - the households are identified.
Sampling rate and sampling size
Concerning the SILC instrument, three different sample size definitions can be applied:
- the actual sample size which is the number of sampling units selected in the sample
- the achieved sample size which is the number of observed sampling units (household or individual) with an accepted interview
- the effective sample size which is defined as the achieved sample size divided by the design effect with regards to the at-risk-of poverty rate indicator
Given that the effective sample size has been already treated in the section dealing with sampling errors, in this section the attention focuses mainly on the achieved sample size.
The necessary sample size for Bulgaria is determined in the Annex II of the Framework Regulation (1177/2003) to guarantee an effective sample size with regard to the at-risk-of-poverty indicator of 4500 households. The longitudinal sample for two successive waves should comprise at least 3500 households.
The total gross sample size (number of households) has been made analyzing the non-response rates and design effects of the previous EU-SILC surveys.
The total sample size in 2018 is 8696 households:
- 6376 “old” (2013, 2014, 2015, 2016 and 2017),
- 2320 “new” households (drawn in 2018).
Number of households for which an interview is accepted for the database.
Rotational group breakdown and total
Rotational group breakdown and total
The sample size for longitudinal component was 25226 households and 52610 persons aged 16 and over.
Number of households in longitudinal component
Number of persons 16 years and older
|Frequency of data collection|
SILC2018 data are collected with questionnaires (CAPI and PAPI) through personal interview with household, including in the sample and all household members aged 16 and more.
The mean interview duration
The mean interview duration per household is calculated as the sum of the duration of all household interviews plus the sum of the duration of all personal interviews, divided by the number of household questionnaires completed. Only households accepted for the database have to be considered.
The average household interview duration was about 23 minutes, while the average individual interview duration was about 22 minutes.
Average interview duration = 67
In the process Data-entry is a logical control of extreme values, filled-in information on all issues, data comparability checks, links between individual questionnaires and registers is carried out. After processing the primary data and receiving the target changes, a verification with the SAS program provided by Eurostat for verification and validation of the data is performed. Additional compatibility checks are performed before publishing the information
The database of each country contains a different types of weights:
Weighting factors were calculated as required to take into account the units’ probability of selection, non-response and to adjust the sample to external data relating to the distribution of households and persons in the target population, such as sex and age, residence or administrative-territorial districts (NUTS 3).
For the first year of the panel each household from the new rotation group got a sampling weight inversely proportional to the probability of selection of the household. These were the household’s design weights DB080.
To adjust for non-responding households the procedure “weighting classes” was used. The households were divided into classes where the probability to respond was assumed to be homogenous within the classes. Due to lack of information (demographic characteristics) for the non-responding households these classes were the sampling strata. The ratio of the weights of the responding households to the weights of all households in the given class was calculated.
After reflecting the non-responding households the base weights for the new rotation group were calibrated to the population as of 31.12.2017. For the calibration the following variables at individual and at household level were used:
The information on individuals as of 31.12.2017 was available from the ISD. The information on the households was an estimation made on the basis of the updated file on Census 2011 and data on the split-off households from the SILC survey. Persons born in 2018 were not included in the calibration as they were not part of the population as of the end of 2017. For the calibration of weights the SAS Macro Calmar 2 was used.
The logit method (M=3 in Calmar) was used for the calibration by setting upper and lower limits of the g-weights. The G-weights were the ratio of the assigned weights and the final calibrated weights. The upper limit in 2018 was 2.5 and the lower – 0.1.
The calibrated weights with reflected non-responding households were the base weights (RB060) for the new rotation group and will be used in the weighting procedure in the following years. These weights were also the longitudinal weights (DB095) of the households from the new rotation group.
Weighting procedure for rotation groups (11, 12, 13, 14, 15) from previous survey waves.
To get the base weights for the current year, the base weights (RB060) for each rotation group from the previous year were adjusted taking into account the non-response. The adjustment procedure was made on an individual and not on household level.
To adjust for non-response first all persons from the 2017 register (DB135 = 1 & RB110 in (1,2,3,4)) who were followed up in 2018 were marked as responding (current members of the household). Persons who have left the household between the two survey waves (2017 and 2018) were marked as non-responding. A logistic regression was used to calculate the probability for each individual to be enumerated between 2017 and 2018. The weights of the enumerated persons were adjusted with the probability of following up (result of logistic regression) and thus the base weights (RB060) for 2018 were get.
The model was applied for each rotation group separately. The independent variables used in the model were: poverty indicators, education, economic activity, age, sex, household size, household type, income, dwelling type. The dependent variable was the one showing if the individual was enumerated or not.
New members of the household after first year who were not part of the sample got base weights for the current year as follows:
· Children born to a sample mother got the weight of the mother;
· Persons who have come into the sample household outside the target population got base weight which was equal to the average base weight of the household members;
· Persons who have come into the sample household from other non-sample household within the target population got base weight equal to 0.
Each person in the household should receive equal weight within the household (RB050 cross-sectional weight). For this reason each household member whit zero and non-zero base weight received average base weight within the household.
After the non-response adjustment procedures each of the 5 rotation groups was calibrated separately to the population as of 31.12.2017 according to the method described above.
The same variables and levels as for the new rotation group were used for calibration.
Combining all (6) sub-samples
After applying all procedures for non-response adjustment and calibration, all sub-samples (rotation groups) were combined together. Each sub-sample separately represented all population of the country. To combine all sub-samples all weights were multiplied an appropriate scaling factor. The scaling factor used was 1/6 for 2018 as there were 6 rotation groups in the panel.
Final cross-sectional weights
Calibration of all rotation groups to current population.
After successfully applying all the procedures the weights were calibrated to the population as of 31.12.2018. The following variables on individual and household level were used for calibration:
(0-15) (16-19) (20-24) (25-29) (30-34) (35-39) (40-44) (45-49) (50-54) (55-59) (60-64) (65-69) (70-74) (75+)
In 2016 the number of pensioners was used as calibration variable for first time.
This variable had 3 levels:
1 - old-age pensions
2 - social pensions
3 - all others(rest of population)
To allocate each person to the correct sub-population data from NSSI was used- number of personal pensions as of 31.12. There were two reasons to use this variable as a calibration variable. First, get better estimation of pensioners and second, to reduce the standard error of the AROPE indicator.
After calibration the final cross-sectional weight DB090 of the household was obtained. The individual cross-section weight RB050 was equal to the corresponding household weight DB090 (RB050=DB090).
The newborn in 2018 were not included in the calibration. They received the corresponding household weight after calibration.
The personal cross-section weight for all individuals aged 16 and more (PB040) was calculated after the age group (0-15) was removed. Only the individuals who have responded (or were imputed) to the individual questionnaire (RB250 in (11,14)) were used. After one more calibration the weight PB040 (personal cross-sectional weight for all household members aged 16 and more) was obtained.