Seasonally adjusted (2005 = 100)

Sales in industry, construction, trade and services - Construction Production Indices
Contact organisation

National statistical institute

Contact organisation unit

"Short-term Business Statistics and Statistics of Transport" Department

Contact name

Adelina Terezova

Contact person function

Chief expert

Contact mail address

2, P. Volov Str.; 1038 Sofia, Bulgaria

Contact email address

[email protected]

Contact phone number

+359 2 9857 454

Contact fax number
Metadata update
Metadata last certified17 June 2021
Metadata last posted17 June 2021
Metadata last update17 June 2021
Statistical presentation
Data description

Construction Production Indices is an important short-term economic indicator of business, which purpose is to measure the monthly changes of the construction production between two comparable periods. This information can be used to analyze the current state of the construction activity in the country, as well as short-term forecast for its future development.

The indices - total and separately for building construction and civil engineering are calculated on the base (2015 = 100) and information on actually hours worked in the construction. The rows of data are non-adjusted and seasonal and working day adjusted. Seasonal adjustment of monthly indices is a statistical method, which eliminates the seasonal component and working day adjustment is an adjustment for variations in monthly data, caused by calendar effects, different number of calendar and working days in the months, national holydays and outliers.

Classification system
  • Classification of Economic Activities (CEA-2008, for international use NACE.BG -2008);
  •  Classification of types of constructions (CC) - the building construction includes construction of residential and no-residential buildings and civil engineering - infrastructure construction of roads, bridges, pipelines, power lines, telecommunication and other construction equipment.
Sector coverage

Production Indices in section F of NACE.BG-2008, Construction - total and separately for building construction and civil engineering, according Classification of types of constructions (CC).

Statistical concepts and definitions

The purpose of Construction Production Indices is to show changes of the production in section Construction - total and separately for building construction and civil engineering, calculated on the base of hours worked, directly employed with construction works. Indices are calculated according to the regulations EC about Short Term Statistics.

Statistical unit

The enterprises of section Construction, according to classification of Economic Activities (NACE.BG -2008).

Statistical population

The sample used is formed on the base of the information from annual reports of all construction enterprises which are observed exhaustively. The survey population includes the construction enterprises with more than 4 persons employed. The sample of the surveyed enterprises is formed 75% from turnover in construction.

Reference area

National level: Data are aggregated and published total of R Bulgaria.

EC level: Eurostat are aggregated and published total of EC and by Member States.

Time coverage

The indices are published from January 2000 to the last month of the reference year.

Base period

All indices are calculated on the base 2015=100.

Unit of measure

Indices, percentage changes (%).

Reference period


Institutional mandate
Legal acts and other agreements

National Legal Basis: The Law on Statistics (Article 20) states that all persons that manage or present legal persons, are obligated to provide the National Statistical Institute and the Bodies of Statistics with reliable data when filling-in forms and questionnaires on surveys included in the National Statistical Programme, for which mandatory participation is provided.

The survey is included into the National Statistical Programme and it is compulsory for enterprises which are included in the sample of survey. The Law on Statistics includes provisions relating to fines, which can be imposed for refusal, non-response and delay. They are laid down in specific Chapter 9 "Administrative and liability provisions" in Article 52.

EU Legislation:

  •  COUNCIL REGULATION (EC) No 1165/98 of 19 May 1998 concerning short-term statistics;
  •  REGULATION (EC) No 1158/2005 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL amending Council Regulation (EC) No 1165/98 concerning short-term statistics;
  •  COMMISSION REGULATION (EC) No 1503/2006 implementing and amending Council Regulation (EC) No 1165/98 concerning short-term statistics as regards definitions of variables, list of variables and frequency of data compilation;
  •  REGULATION (EC) No 1893/2006 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 20 December 2006 establishing the statistical classification of economic activities NACE Revision 2 and amending Council Regulation (EEC) No 3037/90 as well as certain EC Regulations on specific statistical domains;
  •  COMMISSION REGULATION (EC) No 472/2008 of 29 May 2008 implementing Council Regulation (EC) No 1165/98 concerning short-term statistics as regards the first base year to be applied for time series in NACE Revision 2 and, for time series prior to 2009 to be transmitted according to NACE Revision 2, the level of detail, the form, the first reference period, and the reference period.
Data sharing

The data are transmitted to Eurostat together with the national publication.

Confidentiality - policy
  •  Law on Statistics;
  •  Regulation (EC) No 223/2009 on European statistics (recital 24 and Article 20(4)) of 11 March 2009 (OJ L 87, p. 164), stipulates the need to establish common principles and guidelines ensuring the confidentiality of data used for the production of European statistics and the access to those confidential data with due account for technical developments and the requirements of users in a democratic society.
Confidentiality - data treatment

Article 25 of the Law of Statistics defines the criteria by which can not be distributed or published statistical information. Statistical information which aggregates data about less than three statistical units or about a population in which the relative share of the value of a surveyed parameter of a single unit exceeds 85 percent of the value of such parameter for all units in the population.

Confidential data, accordance with the Law of statistics not publish. In order not to identify individual data using the method of suppression or aggregation of information disclosed.

Release policy
Release calendar

The date for publication of statistical information is given in the Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute, which is available on NSI website. The indices of construction production are published 37 - 40 days after the reference month.

Release calendar access

The calendar is available on the NSI website:

User access

The data are published on the NSI website, section Business statistics - Short-term Business Statistics - Monthly date in accordance with the Law on Statistics and the European Statistics Code of Practice respecting the professional independence and aimed at objectivity, transparency and equal treatment of all consumers.

Frequency of dissemination

Every month.

Accessibility and clarity
News release

Press release of Indices Production Construction are published 37- 40 days after the end of the reference month on the NSI website.


Brochure 'Bulgaria'

On-line database

Data on indices of construction production are available to all users on the NSI website under the heading Statistical data - Business statistics - Short-term Business Statistics - Monthly data - Construction Production Indices: or in the on-line database INFOSTAT.



Micro-data access

Not applicable.


Not applicable.

Documentation on methodology
Quality documentation

Regulation (EC) № 1165/98 and amending Regulation (EC) № 1158/2005 Short-term statistics obligate the European Commission (Eurostat) regularly (every three years) to report in the Parliament of Europe applicability of short-term data quality and revisions of the data.

Quality report of Eurostat from 2008 Principal European Economic Indicators (PEEI in focus), containing information on the calculation of Indices Production Construction in European countries.

Quality management
Quality assurance

The legal framework which regulates the production of data from Short-term business statistics states that statistical data compiled within the EU system must be of satisfactory quality and produced data are comparable between Member States. Verification of data is done through the process of conducting a statistical survey - from respondents, from experts in the regional statistical offices and from national experts in NSI. Identified inaccuracies and errors are removed timely and provide comparable data of good quality.

Quality assessment

The quality of the short-term indicators is measured by each Member State in accordance with the general criteria. Calculation of the variables is carried out in accordance with EU Regulations on Short-term business statistics.

User needs

Eurostat, the state governing bodies, associations, businesses, media and others users.

Internal users - Department 'Macroeconomic statistics'.

User satisfaction

No information.


The necessary statistical data are provided on the required level of detail, accordance by the relevant STS Regulations.

Accuracy and reliability
Overall accuracy

The general population includes about 21 000 enterprises, of which is formed survey population of more than 6 000 construction enterprises, with more than 4 persons employed. Monthly sample includes about 2 150 enterprises, which formed about 75% from the turnover of construction enterprises.

The sample method used is Stratified Random Sample. Criterion for stratification of the enterprises is 'number of persons employed'. First enterprises are stratified by groups (2-nd digit level of NACE.BG 2008) and then in each group they are stratified by number of persons employed. Enterprises with 30 or more persons employed are surveyed exhaustively. The enterprises with employed from 5 to 14 and from 15 to 29 employed are randomly sampled.

Is ensured a maximum accuracy and reliability of the data from the enterprises included in the monthly sample in section Construction.

Common errors are errors in the measurement data, the respondent misunderstanding what information is required or incomplete performance.

Most measurement errors are detected and corrected by arithmetic and logical controls embedded in Information System "Short-term business statistics" (On-line information system for collection, verification and processing of data from short-term business statistics). The system performs mandatory and planned control and warning in case there are errors, it displays a warning dialog inconsistencies found. The system does not allow the completion of the report until all outstanding correct mandatory controls.

Sampling error

In the sample of construction firms use the method of 'Stratified random sampling'. To ensure the accuracy of the sample is calculated coefficients of variation and the standard errors are within acceptable limits.

Non-sampling error

Using programs SPSS, Excel and thorough analysis of the data did not allow the emergence of problems such as excessive coverage, inadequate coverage and repeated entries. For non-response methods are used to update the sample - like editing and imputation data.

Actions for non-responders include: informing and sending reminders, when no-responding company may follows a phone call and / or direct contact to collect the data. The responding rate is average approximately 90%.

Timeliness and punctuality

The indices of construction production are published 37 - 40 days after the reference month.


All data rows, tables, and press releases are prepared and submitted for publication, accordance STS Regulations and within the deadlines specified in the calendar for publication of data. NSI sent data to Eurostat on the day of national publication.

Coherence and comparability
Comparability - geographical

Construction Production Indices are representative for the whole country and have no representation by regions. The implementation of the EU requirements and national methodology for calculating the Indices of Production in Construction ensures data consistency between Bulgaria and other European countries.

Comparability - over time

Time series published from 2000.

Coherence - cross domain

Data from the monthly statistical survey about hours worked, which is used to calculate the indices of production in construction, are checked with other variable - data for sales (monthly and quarterly) from construction enterprises.

Coherence - internal

Comparisons are made with the final figures for construction production from the Annual Business Statistics.

Cost and burden

No information on the relationship between cost of production of statistics data and user satisfaction. The purpose to reduce response burden is created on-line information system 'Short-term business statistics' (IS STS).

Data revision
Data revision - policy

Construction Production Indices usually suffered two revisions. Each month data for the reference month are published as a preliminary and data for the previous month as a final. At the beginning of the year, the indices for the previous year are reconciled on the basis of exhaustive annual data from Annual Business Statistics.

Data revision - practice

Minor changes are made at the time when the revision is introduced and they are marked in footnotes in the relevant published tables.

The revised data are published on the NSI and transmitted to Eurostat.

Statistical processing
Source data

Information for calculating the indices of construction production - total and separately for building construction and civil engineering provides from 'Questionnaire about hours worked from directly employed in construction enterprises', included in the monthly report 'Main short-term indicators'.

Frequency of data collection

Every month.

Data collection

For the convenience of respondents and getting better and timely information is created on-line information system (IS STS). The system controls are set to ensure the accuracy of the information. Possibility remains that the respondent submits monthly report and a paper in the relevant regional statistical office. Delay on the part of businesses IS STS send reminders. Experts from RSOs phone calls to provide timely information or clarification of the data.

Data validation

Validation data starts from the filling of reports by respondents. Control of the data can be accessed from both the regional statistical offices and from experts in the National Statistical Institute. An information system 'Short-term business statistics' significantly contributes to the validation of the data submitted by set arithmetic and logical controls. Subsequent analysis of the experts, a phone call for further clarification of data and elimination of disparities, minimize errors in the raw data and ensure accuracy of outputs at national level.

Data compilation

Construction Production Indices are calculated based on the information of construction businesses total hours worked and separately for building and civil engineering on paper or on-line via the information system 'Short-term business statistics'. After validating the data by the regional statistical offices, then the deadline for entry, by experts in the NSI, the data from construction enterprises in the sample are extrapolated and calculated indices of construction production on the national level.


In accordance with Regulations concerning STS, the Construction Production Indices are to be seasonally and working day adjusted. The software used for seasonally and working day adjustment is JDemetra +. The method used is TRAMO-SEATS.

The purpose of working day adjustment is to check and eliminate the significance of the calendar effects as the results from the difference in the number of working days and holidays in the national calendar.

The purpose of seasonal adjustment is to remove ordinary seasonal variation. The series of data are checked for outliers of different types and typical calendar effects on the dynamics of a given indicator. Usually seasonal fluctuations are those changes that are repeated seasonally each year.

Time series the indices of building construction and civil engineering are seasonal and working day adjusted, and time series of the indices of construction - total obtained by applying the indirect method.

Revisions of seasonally and working day adjusted data are published in accordance with accepted revision policy and release calendar for the unadjusted data.

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