Retail trade

Period: Annual
Year: 2021

01. Contact
02. Metadata update
03. Statistical presentation
04. Unit of measure
05. Reference Period
06. Institutional Mandate
07. Confidentiality
08. Release policy
09. Frequency of dissemination
10. Accessibility and clarity
11. Quality management
12. Relevance
13. Accuracy and reliability
14. Timeliness and punctuality
15. Coherence and comparability
16. Cost and Burden
17. Data revision
18. Statistical processing
19. Comment

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01. ContactTop
01.1. Contact organisation

Statistical Office of the Republic of Serbia (SORS)

01.2. Contact organisation unit

Domestic Trade, Catering Trade and Tourism Statistics Division

01.3. Contact name

Danijela Mladenović

01.4. Contact person function

Statistician methodologist

01.5. Contact mail address

Milana Rakića 5, Belgrade

01.6. Contact email address

01.7. Contact phone number


01.8. Contact fax number


02. Metadata updateTop
02.1. Metadata last certified
02.2. Metadata last posted
02.3. Metadata last update

03. Statistical presentationTop
03.1. Data description

The main purpose of data collecting is providing the indicators on turnover in retail trade on monthly basis. Data are collected by statistical surveys Monthly Report on Retail Trade (Form TRG-10) and Quarterly Survey on Retail Trade (Form TRG-16) and by using administrative data (Tax Administration data from Value Added Tax).

The objective of the retail trade turnover index is to show the development of the consumer goods market and measure the change of retail sales. As an important short-term indicator, retail trade turnover index is used to analyse economic situation and as an indicator of individual consumption and input for National accounts statistics.

Indices on the retail trade turnover are presented in two ways:

·  for retail trade turnover including VAT (for national purposes);

·  for retail trade turnover excluding VAT (obligations according to Eurostat).

Indices on retail trade turnover are calculated and computed at current and constant prices. Indices at current prices are nominal indices that present trend of turnover value between the two periods. Indices at constant prices are real indices obtained by deflating indices at current prices with the corresponding consumer price indices.

03.2. Classification system

- Classification of activities CA (“Official Gazette of RS”, No 54/10), which is without any changes based on Statistical Classification of Economic Activities in EU – NACE Rev. 2.

- National Nomenclature of Statistical Territorial Units (“Official Gazette of RS”, No 109/09 and 46/10)

03.3. Coverage - sector

Statistical surveys involve:

- enterprises (legal entities) whose principal activity is classified in Retail trade, excluding trade of motor vehicles and motorcycles (division 47);

- selected legal entities whose principal activity is classified in other CA sections, but they realize significant turnover in retail trade as secondary activity.

Administrative data source – included are unincorporated enterprises registered in value added tax system (VAT payers) within the section of Retail trade, excluding trade of motor vehicles and motorcycles (division 47 of CA), as well as bakeries and butchers.

03.4. Statistical concepts and definitions

Main statistical variable is turnover. Data collected refer to retail trade turnover including VAT and the amount of VAT which are calculated on invoiced turnover (included in the sales price to customers).

Turnover excluding VAT (for Eurostat needs) is derived from these two variables.

Retail trade turnover represents the sales of goods to final consumers (primarily to individuals for personal consumption, for use in the households, as well as to other consumers who are supplied at retail prices). The turnover of goods in retail trade also includes the sale of goods to individuals through consignments, whether performed from a warehouse or a store.

Retail trade turnover comprises the invoiced value from sales of goods during the reference period, no regardless it was paid or not. Turnover includes excise duties and excludes income from sales of fixed assets, as well as other operating income, financial income and other extraordinary income (rentals, subsidies, etc.).

Deflated turnover presents turnover at constant prices.

Indices in retail trade turnover are calculated with VAT (for national purposes) and without VAT (for Eurostat), in accordance with concepts and definitions from Eurostat Regulations that refers to short-term business statistics.

03.5. Statistical unit

Reporting unit is an enterprise.

Statistical observation units are enterprises with principal activity classified under Division 47 of CA as well as KAU (kind of statistical unit) for enterprises not classified in CA division 47, but such units perform significant retail trade turnover.

Administrative data source - Tax Administration is the reporting unit; statistical observation units are VAT returns of unincorporated enterprises performing retail trade activity.

03.6. Statistical population

The target statistical population includes all active businesses entities with principal activity classified in Retail trade, excluding trade of motor vehicles and motorcycles (Division 47 of NACE Rev. 2). Also, statistical population includes certain number of business entities that perform retail trade, but according to principal activity they are classified in other activities.

Legal entities are surveyed in monthly and quarterly surveys, based on random samples. The goal of the monthly survey is to present trend tendency of retail trade turnover, for the level of statistical territorial units (Republic of Serbia, Srbija – Sever, Vojvodina, Srbija – Jug) and activity branches by CA. The monthly sample is a subsample of the quarterly survey. The quarterly survey, conducted on a larger number of units in the sample provides final results.

The sampling frame for both surveys is based on statistical business register (SBR) which includes about 7000 enterprises in retail trade activity that have reported annual financial statements (for the year t-2, where t is the reference year). The sampling frame was constructed from this list of enterprises by excluding the smallest enterprises. Annual turnover and size class of the enterprise are used as size measure. Included are all large and medium enterprises, as well as small enterprises with annual turnover of more than 4 million RSD. Annual turnover and size classes (large, medium, small and micro) for enterprises are taken from financial statements for the year t-2, where t is the current year. Size of the enterprise is defined according to the annual turnover, number of employees and assets of the enterprise. Excluded enterprises make up less than 1% of turnover. The sampling frame includes about 4250 enterprises out of which 43 of them are not registered in retail trade as their principal activity.

The number of enterprises in the population and the sampling frame according to NACE Rev. 2 classes or groups in retail trade activity presented in the Table below.

Table 1. Number of units according to NACE Rev.2 classes or groups in 2021

NACE Rev 2. - class or group


Sampling frame



































Coverage of unincorporated enterprises performing retail trade activity is based on VAT returns received from Tax Administration.

In 2021, the average number of monthly VAT returns obtained for the retail trade activity (division 47 of NACE Rev. 2) and bakery and butcher shops involves about 7000 unincorporated enterprises, while the average number of quarterly VAT returns accounted about 7800 unincorporated enterprises.

03.7. Reference area

Republic of Serbia

Note: Starting from 1999 the Statistical Office of the Republic of Serbia has not at disposal and may not provide available certain data relative to AP Kosovo and Metohija and therefore these data are not included in the coverage for the Republic of Serbia (total).

03.8. Coverage - Time

Comparable time series of retail trade indices are available from January 2000 onwards. Time series for the period 2000-2010 were recalculated in accordance with NACE Rev. 2 classification, so the time series can be considered continuous.

03.9. Base period

In accordance with Eurostat Regulation for short-term indicators, indices are computed on 2015 base year.

Monthly indices of retail trade turnover are issued relative to “the same month of the previous year”, “previous month” and “the same period of the previous year”.

Moreover, calculated and issued are the corresponding indices on quarterly and annual level.

04. Unit of measureTop
04. Unit of measure

Data on turnover are collected in thousand RSD.

Only indices (at current and constant prices) in monthly and quarterly periodicity are disseminated. On annual level, absolute figures are also issued.

05. Reference PeriodTop
05. Reference Period

The data are collected on monthly (preliminary results) and quarterly basis (final results).

Reference period is a calendar month and a calendar quarter.

06. Institutional MandateTop
06.1. Institutional Mandate - legal acts and other agreements
National legislation
- Official Statistics Law
- Resolution on the Programme of official statistics
- Regulation on the Plan of official statistics for the current year
* The above documents are available at SORS website:
Important legal acts and other documents at the European Union level:

The European Parliament and Council adopted the European Business Statistics (EBS) Regulation (EU) 2019/2152 on 27 November 2019, followed by the Commission Implementing Regulation 2020/1197 laying down technical specifications and arrangements pursuant to the mentioned EBS Regulation (General Implementing Act).

The former legal basis for the STS indicators is the Council Regulation No 1165/98 of 19 May 1998 concerning short-term statistics and subsequent amending regulations.

A consolidated version of the EBS Regulation can be found on the Eurostat website. 

06.2. Institutional Mandate - data sharing

Data on retail trade turnover (VAT excluded) at current and constant prices are transmitted to Eurostat via eDamis, in regular monthly periodicity, in the form of original indices, seasonally adjusted indices and working-day adjusted indices.

07. Confidentiality Top
07.1. Confidentiality - policy
Data confidentiality is stipulated by:
- Official Statistics Law (Official Gazette of RS, number 104/2009), Articles 44, 45, 46, 47, 48, and 49. 
- Rulebook on statistical data protection in the Statistical Office of the Republic of Serbia
( and
- Guidelines on measures of data and information protection in the Statistical Office of the Republic of Serbia

European legislation: Regulation (EC) No 223/2009 of the European Parliament and of the Council of 11 March 2009 on European statistics.

07.2. Confidentiality - data treatment

Confidential data may be used for statistical purposes only. Confidential statistical data are individual data as well as aggregates on which the data holder may be recognized in any way.

Confidential data are considered official secret and cannot be published or communicated, that is, they cannot be part of aggregated data from which individual data can be identified.

When processing confidential data for users’ needs, data protection must be provided so that individual data cannot be identified on either level of aggregated data.

08. Release policyTop
08.1. Release calendar
Calendar of releases is available at SORS website on the 1st day of December every year for the forthcoming year (
All SORS releases are launched at 12.00. Any divergence from the defined time schedule are announced in advance and explained in the Calendar.
08.2. Release calendar access

Calendar of releases is avaliable at SORS website:

08.3. Release policy - user access
The data obtained through statistical surveys are released at the internet presentation (, in the database (, in statistical releases and publications ( 
The results of official statistics are available at the same time to all users on impartial basis; any privileged access by external users before their release is not allowed.

09. Frequency of disseminationTop
09. Frequency of dissemination

Retail trade turnover indices at current and constant prices are issued monthly.

10. Accessibility and clarityTop
10.1. Dissemination format - News release

Data on retail trade turnover are published in monthly periodicity, in Statistical release ‘’Retail trade turnover’’, on SORS website simultaneously, in Serbian and in English, according to Release calendar.

Domestic trade turnover data are published in Statistical release on a quarterly basis. The data sets are published for Divisions 45, 46 and 47 of the Classification of Activities.

10.2. Dissemination format - Publications

“Monthly Statistical Bulletin” - statistical data are presented in quarterly and monthly series, by the territorial level and by Classification of Activities. Monthly series comprise period of the last 13 months;

“Trends” - a quarterly publication providing information on current trends in economy;

“Statistical Yearbook of the Republic of Serbia” - an comprehensive annual publication compiles all final data and series of the most important indicators from different areas of economic and social life of the country;

“Statistical Pocketbook of the RS” - an edition that offers the principal statistical data on national social and economic development.

10.3. Dissemination format - online database

Retail trade data (monthly, quarterly and annual indicators) are available in the Statistical Database in scope of the statistical area of Domestic Trade:

10.4. Dissemination format - microdata access

Micro-data are not disseminated to users.

10.5. Dissemination format - other

Monthly indices on retail trade at current and at constant prices, seasonally adjusted and working-day adjusted indices are transmitted monthly to Eurostat, starting from the first month of 2000, in accordance with the requested level of details, deadlines and required form.

On users’ request, SORS may provide the data and information obtained by special processing.

10.6. Documentation on methodology

Methodological explanations (referent metadata) and statistical questionnaires on retail trade are available on the website:;

10.7. Quality management - documentation

11. Quality managementTop
11.1. Quality assurance
The SORS quality management system is relied on the Serbian official statistics mission and vision, as well as on the European Statistics Code of Practice – CoP and the Total Quality Management – TQM principles, which together make the common quality framework of the European Statistical System (ESS).
For more information, please see the documents at
11.2. Quality management - assessment

Data quality and surveys’ conducting are monitored throughout all stages of data production, by the responsible statisticians, sample and time series experts, according to specifications for concrete surveys, and quality is at a very satisfactory level.

Statistical activities are directed to monitoring of the main quality aspects in scope of statistical surveys’ organization (data collection, coverage, data processing, punctuality and timeliness).

12. Relevance Top
12.1. User needs

The main data users are state administration bodies (Government, Ministry of Trade, Tourism and Telecommunications, Ministry of Finance), Chamber of Commerce, business entities, economic analysts, media representatives, researchers, students, internal users (National accounts statistics, Prompt and complex reporting and public policies support division), international users (Eurostat, IMF).

12.2. User satisfaction

On biennial basis (once in two years), by the means of web interview, implemented is the User Satisfaction Survey. The survey results are available at SORS website:


12.3. Completeness

All statistics according to Eurostat STS Requirements are available.

13. Accuracy and reliabilityTop
13.1. Overall accuracy

The retail trade turnover is computed by combining estimates on turnover from statistical surveys (enterprises) and administrative data (enterpreneurs).

Enterprises (legal entities)

The main error sources in statistical surveys are of sampling and non- sampling nature.

The surveys are based on random sample. Sampling frame is constructed using enterprise data from the Statistical Business Register (SBR).

The sample design is such that the estimates for the main domains are of satisfactory precision.

The following non-sampling errors are present:

· coverage errors due to not completely updated SBR and existing time lag in registering the changes of enterprise units;

· errors that are a consequence of cut-off sampling, smallest enterprises are excluded from the sampling frame;

· measurement and non-response errors that are inevitable, but the instruments of data collection, organization and data entry are such that they are reduced to the lowest possible level.

The general assessment is that the type, design and organization of the surveys, as well as the data collection and processing methods ensure sufficient overall accuracy.

Unincorporated enterprises (Entrepreneurs)

Since data on turnover of unincorporated enterprises are derived from VAT returns, obtained from Tax Administration, unincorporated enterprises (entrepreneurs) which are not obliged to VAT calculating are not covered.

For quarterly VAT payers, monthly turnover values are estimated (for each month of the quarter).

The data (results) are final 60 days after the reference quarter for the months of that quarter, after quarterly data revision, when the preliminary results obtained on the basis of the monthly survey are replaced with final data from quarterly survey (t+60) that is carried out on a larger number of units in the sample and when data from Tax Administration for quarterly taxpayers are available.

13.2. Sampling error

The sample design is such that the estimates for the main domains are of satisfactory precision.

The sampling weights are corrected for non-response and for the presence of outliers.

Coefficients of variation are calculated for estimated monthly turnover and chain index in retail trade by NACE Rev. 2 classes and groups, as well as for NUTS 2 regions.

For the total monthly turnover, estimates of the coefficients of variation are about 0,7%. On the level of the Republic of Serbia, coefficients of variation of chain indices in retail trade are around 0.3%.

The monthly average of the coefficients of variation for the chain indices is highest in class 47.9 (3.17%) and 47.5 (2.3%). The monthly average of the coefficients of variation for the chain indices is lowest in class 47.8 (0.0%), group 47.11 (0.21%) and class 47.3 (0.21%).

The response rate is high throughout the whole year. Тhe un-weighted response rate on the level of the Republic of Serbia is between 86.9% (January) and 93.1% (June). Size-weighted response rate in 2021, on the level of Republic of Serbia, on average is 98.6%, the size-weight is the product of design sample weight and a size measure, reported turnover in retail trade in the given month. Based on the results for 2021, the size-weighted unit response rate on the level of the Republic of Serbia is between 96.58% (January) and 99.02% (November).

In the Annex is a table with monthly estimates of coefficients of variation by main economic classes in retail trade.

 Annexes :
 Sampling error
13.3. Non-sampling error

Enterprises (legal entities)

Non-sampling errors can arise in all stages of survey activities. Non-sampling errors can arise due to: coverage errors, non-response, measurement and processing.

Frame imperfection is the major cause of coverage errors. SBR variables: the economic activity of the enterprise, registration status and turnover from the financial statement for the year t-2 are of crucial importance for the definition of the survey sample design and sample selection. If these variable values are not updated, or with an error, then coverage errors may occur.

In addition, the under-coverage errors arise because the frame lists contain only the data on enterprises that have submitted the financial statements for the year t-2. Those that opened after that year are not covered unless it is known that they are exceptionally big or important for the activity they perform. Under-coverage errors are also caused by exclusion from the sampling frame the smallest enterprises with respect to turnover (from financial statements for the year t-2).

Although the magnitude of the under-coverage error is not computed it is not considered to be significant.

The over-coverage and non-response errors (or the rate of response) are computed using the coded information on response that is classified in 9 categories:

1. Runs business, submits report;

2. Runs business, refuses to submit a report;

3. Not found (undeliverable questionnaire);

4. Closed, extinguished;

5. Blocked, not working;

6. Outside the scope of survey (does not perform selected activity);

7. Bankruptcy;

8. Liquidation;

9. Other reasons (e.g. unknown reason of non-response).

Over-coverage units, determined not to belong to the target universe for the survey, are those for which the coded information on response is 4, 5, 6, 7 or 8. The average rate of over-coverage was 7.08% in 2021. On the level of the Republic of Serbia, the over-coverage rate is between 5.19% (January) and 8.82% (December). The main reasons for over-coverage are ‘not working’ and ‘outside the scope of the survey’.

Non-response units are in-scope units for which data were not collected. Non-response units are those for which the response code is 2, 3, or 9. The average (un-weighted) non-response rate was 8.08% in 2021. On the level of the Republic of Serbia, the un-weighted non-response rate is between 6.89% (June) and 13.14% (January). Size-weighted unit nonresponse rate (size-weight is the product of design sample weight and a size measure, reported turnover in retail trade in the given month) on the level of Republic of Serbia is between 0.98% (November) and 3.42% (January).

In order to reduce the non-response, the following measures are undertaken: web questionnaire is introduced, e-mail and written remainders are sent, reporting units are contacted by telephone,  Once a year, a new coordinated sample with rotation is selected. In this way, a gradual replacement of small sampling units is provided, among which non-response is frequent. Every effort is made to reduce non-response to a minimum.

In order to reduce measurement and processing errors, the following measures are undertaken: collected data are entered in the application that represents the so-called "controlled entry". During this phase, the program does not allow the entry of numerically inconsistent data. The next step is to run the program for checking logical inconsistencies. Further steps in data editing are based on the analysis of statistical experts and resulting with correction of discovered errors. If necessary, the reporting unit is contacted in order to get correct data. Finally, data validation is realized during analysis of the aggregates.

In the Annex are tables with monthly un-weighted over-coverage and both un-weighted and size-weighted unit non-response rates by main economic classes in retail trade.

Unincorporated enterprises (Entrepreneurs)

VAT returns obtained from Tax Administration are used for estimation of entrepreneurs’ turnover.

Under-coverage is caused by small units which are not VAT payers, but it is expected that it does not have a significant impact on total retail trade turnover index.

Analysis of administrative data is focused on the quality of data from the tax return of value added tax. The tax data are thoroughly checked, both for individual months/quarters as well as over months and quarters. Turnover and VAT values of entrepreneurs are sorted in the decreasing order to detect values that are suspicious for errors. For those values that are suspected to be with errors, further checks are conducted by comparison with the data from the previous months/quarters.

 Annexes :
 Non-sampling error

14. Timeliness and punctualityTop
14.1. Timeliness

Preliminary results of retail trade are published on the last day in a month for the previous (referent) month. Preliminary data are corrected by using the final monthly data of the quarterly survey (t+60) that is conducted on a larger number of units in the sample.

14.2. Punctuality

There is no time lag between the actual delivery of the data and the target date when it should have been delivered. Deadlines are respected and data are published and delivered on time, according to the pre-announced Release calendar.

15. Coherence and comparabilityTop
15.1. Comparability - geographical

The same statistical concepts are applied for the entire territory.

15.2. Comparability - over time

The time series of the presented indicators are comparable over time.

15.3. Coherence - cross domain

Data from Monthly report on retail trade are compared with the data from Quarterly Survey on retail trade and completely coherent.

Comparison with VAT data does not indicate major discrepancies between available data from administrative sources and results of the survey.

Occasionally, comparisons with other statistical sources covering turnover, quarterly Structural Business Statistics data, are carried out, but it should be noted that there are certain methodological differences and some differences in definitions.

The results of retail trade are used as an input data for the creation of Quarterly National Accounts.

15.4. Coherence - internal

Retail trade data are internally coherent. In order to check the internal coherence, comparison is carried out between the data of the previous month and data of the reference month, as well as comparison of the current data with the data of the corresponding period of the previous year.

All aggregated data are derived on the basis of individual data.

16. Cost and BurdenTop
16. Cost and Burden

Standardized information on cost and burden is not systematically collected.

A system of coordination of random samples of business entities has been introduced, which reduces the burden of small units.

17. Data revisionTop
17.1. Data revision - policy
The SORS general revision policy constitutes the global frame ensuring that each statistical domain shall define its own revision policy in compliance with its specific nature. 
The general SORS revision policy determines:
- general rules of revisions of the published data,
- forms of informing users as regards the possible causes of revisions,
- categories of revisions, and
- documents covering all aspects of revisions.
The general SORS revision policy is available at
The same revision policy is applied nationally and in transmissions of the data to Eurostat.
Comparison and analysis of preliminary and final retail trade turnover data are regularly conducts. Also, comparisons are  made with monthly and quarterly data from the Tax Administration database.
A revision calendar does not exist.


17.2. Data revision - practice

Routine revisions - all published Retail trade turnover indices in Monthly statistical release are treated as preliminary, meaning that certain corrections can appear on the basis of the estimated results, obtained from the regular quarterly survey that are conducted on a larger number of units in the sample. Also, every detected error is corrected on that occasion, as well as any correction, initiated by data providers is performed. Routine revisions are made when preliminary results from monthly survey are replaced with final data from quarterly survey and when the Tax Administration database is completed with data for quarterly tax payers. Retail trade turnover are usually revised four times a year (each time for the months which belong to the specific quarter).

Regarding seasonally adjusted indices, by adding new data, the whole series is updated.

Major revisions that are performed due to changes in CA (2010) or changed base year, performed is so-called back casting in order to obtain comparable data series. Explanations are provided at the time of data publishing or when data dissemination is performed.

The Mean Revision (MR) and Mean Absolute Revision (MAR) are provided as revision quality indicators. They are calculated for year-on-year growth rates for unadjusted and calendar adjusted data.

The computed values for the last 36 months (for the period January 2019 – December 2021) for Retail trade turnover index (excluding VAT) – total are:


Retail trade turnover indices at current prices

Retail trade turnover indices at constant prices






Unadjusted data





Calendar adjusted data






18. Statistical processingTop
18.1. Source data

Combination of statistical surveys (for legal entities) and administrative data source (for unincorporated enterprises) is used.

Enterprises (legal entities)

Retail trade statistical surveys are based on a random sample with a stratified sample design.

The sampling frame is based on the data of the Statistical Business Register, as of 31st of December of the previous year. Stratification of the sampling frame is done according to economic activity of enterprise, size classes according to financial statements and amount of annual turnover.

Stratification according to economic activity of enterprises is into 2 classes (47.11, 47.19), 8 groups (47.2, 47.3, 47.4, 47.5, 47.6, 47.7, 47.8, 47.9), and into one special class reserved for those enterprises whose principal activity is not retail trade.

Stratification according to size of the enterprise is into large, medium, small and micro. Size classes are taken from financial statements and they are defined according to the annual turnover, number of employees and assets of the enterprise.

Within each class defined by cross classifying size class and economic activity group/class, enterprises are further stratified into 2 classes according to the annual turnover: larger and smaller. Units with largest turnover; large and medium units by size and those with businesses related to retail trade, but with the principal activity outside retail trade, presented census units. A random sample is selected from strata marked as ‘smaller’, all other strata are census strata, their units are completely enumerated.

Allocation of sample was done using the Bethel algorithm (Bethel, J. “Sample allocation in multivariate surveys”, Survey methodology, 15, 1989: 47–57) which is based on a Neyman`s allocation method. Turnover was used as the auxiliary information. In this way, a sample of 1918 units was allocated for quarterly survey and sub-sample of 578 units for monthly survey.

A sample of enterprises was selected using the SORS system of coordination that is based on the Swedish SAMU system (SAMU, 2003). In this system, every unit has its unique permanent random number from uniform (0,1) distribution. This number is used in sequential simple random sampling inside each stratum. The starting point for selection was 0.25.

Table, below, includes data on sample sizes, sample fractions and net samples by NACE Rev.2 classes or groups.

Table 2. Sample size, sample fraction and net sample size for the year 2021

NACE Rev 2. - class or group


Sample fraction (%)

Average net sample size (%)














































Unincorporated enterprises

In order to provide data on retail trade turnover from unincorporated enterprises, administrative source are used, i.e. VAT returns obtained from Tax Administration.

18.2. Frequency of data collection

For statistical surveys, periodicity of data collection is monthly and quarterly.

Data from the Tax Administration (VAT returns) are available in monthly periodicity for large taxpayers and in the quarterly periodicity for small taxpayers.

18.3. Data collection

In statistical surveys, data are collected by post (questionnaires), web questionnaires, mail and fax.

The questionnaires used in the surveys are Monthly Retail Trade Report (TRG-10 form) and Quarterly Retail Trade Report (TRG-16 form). Deadline for delivery of the completed questionnaire is the 15th calendar day following the end of the reference month (monthly survey), i.e. 15th calendar day following the end of the reference quarter (quarterly survey).

Actions taken to speed up or increase the rate of response are written reminders sent by e-mail and mail, usually 1-2 days after the time given for the replies. There is also re-contacts by phone. In the monthly survey, data collection is closed 25 days after the end of the reference month.

Data from VAT returns from Tax administration is downloaded via FTP (File Transfer Protocol) server.

18.4. Data validation

There are the following stages of data validation: control of individual data (at micro level) and control of aggregated data and indices.

In order to ensure data quality, simultaneously with collecting and coding, data are visually checked by statisticians for missing, invalid or inconsistent questionnaires or values, and if needed, the reporting units are contacted for additional clarifications. Afterwards, checking is done during the process of data entry and during data processing. Data checking is performed in accordance with the defined criteria of logical and computer control within IST application (statistical information system fully developed in SORS) and error corrections are carried out.

Data are compared with the previous period of the same year, as well as with same period of previous year. If necessary, the respondents are contacted in order to clarify the deviation and correct recognized errors. There is the remark field in the questionnaire for any remark and note with the explanation of the unit (especially in case of large increase or decrease in turnover relative to the previous period).

Possible deviations, observed during the estimation of totals by the sample experts are also checked subsequently.

Statistical results (aggregated data) for the reference month are also compared to the results of the previous month and with the corresponding month of the previous year at each level of aggregation.

The prepared indices are also checked in detail before publication and data transmission to Eurostat.

18.5. Data compilation

The methods used to treat non-response:

imputation for large non-respondents is based on the previous values for the same enterprise or value of the previous periods adjusted by the growth rate of the equivalent period of the previous year; the other units are treated by re-weighting (weights are adjusted to take account of non-response).

The estimations of totals are calculated pursuant to standard procedure for stratified random sample (Horvitz-Thompson estimates). This means that estimates of totals are calculated by summing the weighted values from the sample. Weight for the units of the same stratum is equal to the quotient of the number of units in the stratum and the number of units in the realized sample in the stratum. The realized sample consists of the units that filled out the questionnaire, for which the data were evaluated and for a part of the over-covered units for which the response information is one of the following: not working; has an activity out-of-scope or bankruptcy. The rest of the units are classified into the unrealized sample. Unrealized sample also includes part of over-coverage units (for reasons of "closed" or "in liquidation") in order to compensate, by number, newly created units that a sampling frame does not contain.

Enterprises that were detected as outliers with respect to turnover are put into special census strata. The weights of the remaining units in the strata from which they originated were corrected.

The retail trade turnover index is compiled as a simple index (value relative). The indices are calculated directly from the data (obtained estimates). The retail trade turnover indices are obtained by deflating the turnover index at current process with the appropriate consumer price index, which exclude: water (from public utility systems), electricity and motor vehicles, motorcycles and parts thereof.

18.6. Adjustment

Seasonally adjusted indices of retail trade turnover are calculated. More information on time – series adjustment is provided in the Annex.

 Annexes :
 Seasonal adjustment

19. CommentTop
19. Comment

No comment.