Reference metadata describe statistical concepts and methodologies used for the collection and generation of data. They provide information on data quality and, since they are strongly content-oriented, assist users in interpreting the data. Reference metadata, unlike structural metadata, can be decoupled from the data.
“Short-term Business Statistics and Statistics of Transport” Department
1.3. Contact name
Restricted from publication
1.4. Contact person function
Restricted from publication
1.5. Contact mail address
2, P. Volov Street, Sofia 1038, Bulgaria
1.6. Contact email address
Restricted from publication
1.7. Contact phone number
Restricted from publication
1.8. Contact fax number
Restricted from publication
2.1. Metadata last certified
11 June 2024
2.2. Metadata last posted
11 June 2024
2.3. Metadata last update
11 June 2024
3.1. Data description
Three Producer Price Indices (PPI) are calculated:
Total producer price index
Producer price index on the domestic market
Producer price index on the non-domestic market
Producer Price Index is one of the main short-term business indicators; it is regarded as one of the important measures of the economic situation in the country. Indices for particular economic activity measure the average change in the prices of industrial products, which are produced and sold by Bulgarian enterprises. This is done on the bases of constant sample of groups of products, produced by the activity and sold on the domestic market or directly exported on the non-domestic market and that sample is representative for total industrial production.
The sources of information are two monthly surveys:
Survey on ‘Producer price indices on domestic market’;
Survey on ‘Producer price indices on non-domestic market’.
3.2. Classification system
Classification of economic activities (NACE Rev.2);
Nomenclature of industrial production (PRODCOM).
3.3. Coverage - sector
The survey covers NACE Rev. 2 Sections B to D and Division E36 excluding Groups 25.4, 30.1, 30.3 and 30.4 and Class 24.46.
Enterprises with annual turnover less than BGN 100 thousand are excluded from the survey.
3.4. Statistical concepts and definitions
The Producer Price Indices measure the monthly change in prices of industrial products produced by Bulgarian enterprises and sold on the domestic market or on non-domestic market. The producer price is the ex-factory price and it includes discounts and other reductions. Excise duties and VAT are excluded. In most cases prices correspond to the prices stated at the moment of the contract. Each specific product is precisely described when first selected and is very carefully identified each month when its price is reported. The products are specified with all price-determining characteristics: (brand, content, material used, nature of the customer). When taking into account discounts, reporting units are asked to specify also the quantity, in order not to have fluctuations due to changes in customer's prices. The producer price indices measure the average of the actual prices received for a fixed basket of products that remains the same from one month to the next and also it attempts to take account of changes in quality by means of price changes. The surveyed prices take account of changes in quality that can be caused by a change in either the physical characteristics of a product or a change in the transaction characteristics.
Prices have to be reported on a fixed date around the 15th day of the reference month.
3.5. Statistical unit
Legal unit (considered as enterprise) is both a reporting and observation unit.
3.6. Statistical population
The frame for identifying observation units for the population is the PRODCOM survey, which covers exhaustively all non-financial enterprises manufacturing industrial commodities and/or rendering industrial services with a specified threshold of receipts from sales of industrial production and industrial services. The sample model ensures 90% coverage of sold production in terms of value at the national level for each NACE Rev.2 class.
The number of units in the population of interest (PRODCOM survey) encompasses about 29 000 units.
3.7. Reference area
All regions of Bulgaria are covered.
3.8. Coverage - Time
The producer price indices on domestic market are available from 2000.
The producer price indices on non-domestic market and Total PPI are available from 2005.
3.9. Base period
2021
Indices (%)
The 15th day of each month.
6.1. Institutional Mandate - legal acts and other agreements
National Legal basis: National Law on Statistics (Article 20) states that all persons that manage or represent legal persons, are obliged 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.
Obligation on units to provide data: The survey is included into the National Statistical Programme – it is compulsory. The Law of 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:Regulation (EU) 2019/2152 of the European Parliament and of the Council on European business statistics, repealing 10 legal acts in the field of business statistics (EBS-Regulation) and the Commission implementing Regulation 2020/1197.
All EU documents following the EBS-Regulation can be found in the STS section on Eurostat’s website under Statistics => Short-term business statistics => Legislation
6.2. Institutional Mandate - data sharing
PPIs are published on the NSI website and the data is available to the users.
PPIs are transmitted to Eurostat at the same time with their national publication. Producer price indices are provided to UN and to IMF.
7.1. Confidentiality - policy
The Law on Statistics includes provisions relating to data confidentiality and protection of secrecy, which are in compliance with the EU legislation and standard European practice. In the Law is stated that individual data received and collected during statistical surveys shall be statistically confidential and shall be used for statistical purposes only. Individual data, obtained for the purposes of the statistical surveys, shall not be used as evidence to the bodies of the executive powers and the judicial authorities. Requirements, obligations and measures for data protection, as well as fines that can be imposed, are treated in separate chapters, namely Chapter 6 on „Protection of secrecy” and Chapter 9 on „Administrative penal provisions”.
7.2. Confidentiality - data treatment
Article 25 of the Law on Statistics specifies the criteria, according to which certain data cannot be made public or released – individual data, data which could be indirectly identified, as well as aggregations of less than three statistical units and/or when the relative share of one parameter is more than 85% of the total volume of this parameter for all population units.
Data, which according to the Law on statistics is confidential, are not published.
8.1. Release calendar
The date for publication of statistical information is listed in the Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute.
Data are simultaneously disseminated to the public through a news release on Producer price indices. Producer price indices are published on the NSI website, after which this data are simultaneously accessible to all users: https://www.nsi.bg/en/content/947/producer-prices-indices-industry
No data produced and disseminated by the National Statistical Institute are provided to government officials outside of the NSI before being disseminated to the public.
The NSI transmits producer price indices – Total PPI, PPI on domestic market and PPI on non-domestic market to Eurostat with the required deadlines (30 days after the end of the reference month) and level of detail.
Indices are also transmitted to various institutes and ministries.
The Producer price indices on domestic market time series (from January 2000), Total producer price indices and Producer price indices on non-domestic market time series (from January 2005) at 2-nd digit and higher level of aggregation of NACE Rev.2 are available on the website of NSI – in the on-line database INFOSTAT: https://infostat.nsi.bg/infostat/pages/module.jsf?x_2=188
10.4. Dissemination format - microdata access
Micro data are neither distributed nor provided to the users.
10.5. Dissemination format - other
The NSI transmits producer price indices – Total PPI, PPI on domestic market and PPI on non-domestic market to Eurostat at the date of the national publication.
Data transmission to Eurostat is performed each month. The transmission is carried out in SDMX-ML format via eDAMIS system.
Dissemination on request: Special tables may be obtained from “Relation with users and e-services” department of NSI.
Producer price indices (Total PPI, PPI on the domestic market and PPI on the non-domestic market) are presented as an index: — base year index (2021=100); — compared with the previous month with that month as the base; — compared with the same month of the previous year with that month as the base.
Producer price indices are published at the Division (2-digit level of NACE Rev. 2), Section (Sections B, C and D of NACE Rev. 2) and MIGs level. Regional data are neither produced nor published.
10.7. Quality management - documentation
Information on PPI quality indicators can be found in the methadata presentaion on the NSI website.
11.1. 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 comparable data of good quality are provided.
The quality of statistical information and its production process is ensured by the provisions of the European Statistics Code of Practice. The documentation on quality management is available on the Internet: https://www.nsi.bg/en/content/15005/basic-page/quality-reports
11.2. Quality management - assessment
The quality assessment of the PPIs is based on quality requirements of the ESS (relevance, accuracy, timelines and punctuality, accessibility and clarity, coherence and comparability). The monitoring of the quality of the indicator, updating survey methodology, self-assessment of survey manager are carried out. The response rate is neat to 100 per cent.
The main quality problems concern the pricing of one-off products, pricing the products with long production cycle and in some cases pricing of industrial services.
12.1. Relevance - User Needs
Main users of the information:
Institutions at European level and Multi-national organizations – Eurostat ECB; UN; IMF; WB; etc.;
Presidency, National Assembly, Ministries, National Bank and other representatives of central and local government;
As a main short-term business indicators that predict the tendencies in inflation rate; PPI can be considered as an early measure of the current inflation process in the economy;
As a deflator for calculation the values at constant prices. Example for deflation in National accounts, or for deflation of industrial production and then for compilation the industrial production index;
As an impartial measure of prices for contractual purposes;
As a short-term indicator required from different international organizations like Eurostat, International Monetary Fund, European Central Bank, that use PPI for international comparisons and economic supervision.
12.2. Relevance - User Satisfaction
Not available.
12.3. Completeness
All levels of aggregation required by the EBS Regulation concerning Producer price indices (Total producer price index, Producer price index on the domestic market and Producer price index on the non-domestic market) are calculated, published nationally and transmitted to Eurostat.
13.1. Accuracy - overall
PPI (domestic and non-domestic market) satisfies the principle of accuracy as it describes development of producer prices.
The data are generally considered to be final at first released, there are no estimates produced or published and PPIs are not subject to revision.
Sampling error is not measured due to complexity of price indices and due to the use of non-probability sampling.
There were negligible non-sampling errors concerning coverage, measurement and processing errors. Most of measurement errors are detected and corrected through the logical and arithmetical controls of the Information system “Business cycles” (Online Information system for data collection, editing and processing of the STS information).
Response rate is near to 100%. In most of the cases missing prices are replaced using relevant techniques.
13.2. Sampling error
Non-probability sampling is applied, so the sampling error is not measured.
The sampling method used in the PPI survey on domestic market involves a three stage sampling process: first PRODCOM-2021 groups, second reporting units and then specific products (transactions) are sampled. Size of the national sample and the correspondence to the coverage defined by the national population of interest. The sample includes 1600 industrial enterprises 920 PRODCOM groups and 7000 specific products (specifications).
The sampling technique applied in the PPI survey on the non-domestic market has two stages – sample of enterprises, and sample of representative products/transactions. The sample includes 630 industrial enterprises (direct exporters of industrial products) 550 PRODCOM groups and 2500 specific products (specifications).
The data are generally considered to be final at first released.
13.3. Non-sampling error
Over-coverage and under-coverage: The sample is panel, the adjustments for closed businesses and for new born big enterprises is made periodically.
Misclassification errors: The misclassification didn’t occur.
Impact of models used in estimation: Model pricing is rarely used in PPI.
Multiple listings: All statistical units in the RSU have unique identification number, so the multiple listing cannot occur.
Measurement and technical errors: The measurement errors caused by the data recording are eliminated by the system of automated checks included in the data collection system (Information system “Business Cycles (IS BC)). Technical errors are often recognized with automated checks during the data editing process. A lot of checks are carried out automatically, but under human supervision. Original data from enterprises for a first time are checked from experts in RSOs. Final checks of data from respondents and the aggregated data analysis are done by responsible experts in Central office.
Data editing is carried out at the level of specification prices, if monthly price movements (compare to the previous month) are outside the range of -15% to + 15% the electronic system automatically warns the responsible expert and these movements must be especially conformed by the enterprises with explanations.
Non-response:
The final unit non-response rate is close to 0%. Missing reports are requested by telephone/e-mail contacts with the contact person of the reporting enterprises.
Missing prices (item non-response): IS BC does not allow data providers to submit data if any price of the questionnaire is missing. If there is missing price in the report the System asks reporting unit to propose replacement product (new product in the same product group, which will replace approximately oldest product on the market). In 2023 average monthly were replaced about 0.8% of the priced specifications. The temporarily missing products are imputed manually or automatically through IS BC. The average monthly imputation rate is less than 0.1%. Further information is in p. 18 – Statistical processing
14.1. Timeliness
The Producer price indices (Total PPI, PPI on domestic market and PPI on non-domestic market) are released 30 days after the end of the reference month according to the Release calendar posted on the NSI website.
14.2. Punctuality
NSI fulfils the timeliness requirements of the EBS Regulation. PPIs are transmitted to Eurostat and published nationally 30 days after the end of the reference month.
15.1. Comparability - geographical
Producer price indices in industry are representative for the whole country; they are not representative for the regions of the country.
To calculate the producer price indices on the domestic and on the non-domestic market NSI applies methodology, which is in line with the international standards.
15.2. Comparability - over time
The monthly indices are presented as time series. Indices are fully comparable over time.
15.3. Coherence - cross domain
Internal consistency of the indicators within the questionnaires is checked by reference to ratios between specification prices. The consistency of results relative to previous years' results is also checked.
The Producer price indices are checked with data from other surveys conducted by the NSI (PRODCOM Survey); comparisons with the CPI are made where it is possible.
15.4. Coherence - internal
PPI sub-indices - PPI on the domestic and PPI on the non-domestic market are consistent and coherent with the Total PPI as Total PPI is calculated from the PPI on domestic market and the PPI on non-domestic market weighted with the turnover structure on the domestic and on the non-domestic market to the total value of turnover at each level of aggregation.
Since the beginning of 2012 NSI has been collecting and analysing information through an online information system.
17.1. Data revision - policy
Data revision policy is consistent with Eurostat recommendations (ESS guidelines on revision policy for PEEIs). According to these recommendations, information about major changes, e.g. in classification, methodology or base year, is provided in prior to the change. Notice about minor changes is given at the time the change is introduced.
The same revision policy is applied to data released nationally and transmitted to Eurostat.
17.2. Data revision - practice
Major revisions like base year changes, major changes in methodology, classification changes are discussed and announced in advance. Explanations on the major revisions are included in advance in the methodology of the indicator also in the respective tables footnotes are added explaining the revisions.
Minor revisions - Producer price indices in industry are usually considered to be final when first released. For this reason both Mean Revision (MR) and Mean Absolute Revision (MAR) are equal to 0 for the original data.
18.1. Source data
Information for calculation of Producer price indices in industry is received on the bases of two monthly surveys on producer prices of industrial products, sold on domestic market and on industrial products sold on non-domestic market. The aim of Producer price surveys is: (1) To compare prices of specific products with equal quality in the two surveyed time periods; (2) In the case of quality change of the surveyed specific products this quality change to be taken into account.
Data collection is based on a representative sample of products.
According to the methodology the sampling method used for domestic producer price index compilation involves a three stage sampling process: first PRODCOM groups are selected, as a second step - reporting units are selected and then specific products (transactions) are selected. The sample method used is probability proportional to size.
Producer price indices on domestic market. The sampling method used involves a three stage sampling process: first PRODCOM groups, second reporting units and then specific products (transactions) are sampled.
The sample of product groups is based on the annual survey of production and sales of industrial products - the PRODCOM survey. A sample of reporting is made for each of the selected PRODCOM groups. These units (enterprises) will participate in the price survey. A probabilistic method - proportional to the size is used to ensure sufficient coverage. The number of the units selected in the sample depends on the degree of industrial concentration of the enterprises from each sampled PRODCOM group.
For each enterprise with the corresponding PRODCOM group that was sampled for price survey, the Price index estimation is based on the sample of specific product (specifications). For each enterprise the selected PRODCOM product groups are desegregated into group of product that show equal price changes and from these groups representative specification (specific products) are selected. The selected specifications reflect in the best way the price changes of the whole group. At that stage of sampling so called ‘purposive sampling’ or ‘expert choice’ is applied. The experts from the selected enterprises choose the price quotations, in other words products with the highest sales volume are selected and long presence on the market.
Producer Price Indices on Non-domestic Market. The sampling technique applied has two stages – sample of enterprises, and sample of representative products/transactions.
The sample of enterprises is made on the bases of annual information on receipts of export sales of industrial enterprises. Enterprises with significant amount of export sales are selected for price survey.
The basic concepts relating to determination of priced products relating to export prices are the same as those applying to domestic prices.
For Domestic producer prices survey the sample includes 1600 industrial enterprises 920 PRODCOM groups and 7000 specific products (specifications).
For Non-domestic producer prices survey the sample includes 630 industrial enterprises (direct exporters of industrial products) 550 PRODCOM groups and 2500 specific products (specifications).
18.2. Frequency of data collection
Monthly
18.3. Data collection
Two questionnaires are used:
Questionnaire on Producer price index on the domestic market
Questionnaire on Producer price index on the non-domestic market
Data collection media:
Online through Information system Business Cycles”;
Paper questionnaire. The questionnaires are sent out to the respondents and collected by regional statistical offices, where the information is entered into IS BC.
18.4. Data validation
Validation of the data in the report:
When recording the data, the Information system carries out obligatory and recommended controls according to set with validation rules.
The system carries out the statutory and warning controls. In case there are errors, it displays a warning dialog error in the report. The system does not allow completion of the report until they have corrected these errors by statutory controls.
Data editing is carried out at the level of specification prices, if monthly price movements (compare to the previous month) are outside the range of -15% to + 15% the electronic system automatically warns the responsible expert and these movements must be especially conformed by the enterprises with explanations.
Validation of the output data:
Output data are verified at group level with regard to the previous month, the same month of the previous year and also with regard to extreme values, if necessary data are validated at the level of statistical units.
18.5. Data compilation
Treatment of missing prices:
Prices for temporarily missing products are handled by one of following methods: (1) asking the enterprise to estimate the missing price, (2) imputing the missing price by the price change for the prices that are available from the same enterprise from the same PRODCOM group (3) imputing the missing price by the price change for a particular comparable product from similar enterprise, (4) imputing the missing price by the price change for the prices that are available in the elementary aggregates, or (5) repeating the last reported price.
When a specific product subject to price monitoring, stop producing, is replaced with a new product from the same product group, which will replace approximately the oldest product on the market. The replacement of specifications basely is made through the chain of elementary indices of the old and of the replaced products.
Adjustment for seasonal products: When selecting the product samples, it is ensured that there are some price data available for each month of the year. This is achieved through working closely with respondents. When the price for a particular seasonal specification is not available, an imputation is made using the short-term price change from a matched sample of specifications from the same product group or enterprise.
The type of index used is a Laspeyres index.
Calculation of the producer price indices on domestic and on non-domestic market
Producer price indices are base weighted (Laspeyres) indices - that is to say they are weighted according to the turnover in the base year, currently 2021. After specification’s price collection from the enterprises, elementary indices (price relatives) are calculated for each specification (price relative – specification price in the current month divided by average price of that specification in the base year). After that price relatives are weighted with sales structure in the base year.
Producer price indices at different levels of aggregation are calculated from successive aggregations in which each level of aggregation uses the arithmetic mean of indices at the level below, duly weighted with sales structure in the base year following the structure of the NACE.Rev.2.
In the weighting system, there are two categories of weights, which depend on the level of aggregation:
At group level – 3-th digit of NACE.BG-2008 indices are calculated as price relatives are weighted with sales structure on the domestic or on the non-domestic market by PRODCOM groups. These weights are received from annual PRODCOM survey in the base year.
Producer price index calculation at higher levels of aggregation is base weighted Laspeyres indices that is to say they are weighted according to the turnover structure on the domestic and on non-domestic market in the base year.
Calculation of Total Producer Price Index
Total producer price index is calculated from Producer price index on the domestic market and Producer price index on the non-domestic market weighted with the turnover structure on domestic and on non-domestic market to the total value of turnover at each level of aggregation.
18.6. Adjustment
Seasonal Adjustment is not applied.
Not available.
Three Producer Price Indices (PPI) are calculated:
Total producer price index
Producer price index on the domestic market
Producer price index on the non-domestic market
Producer Price Index is one of the main short-term business indicators; it is regarded as one of the important measures of the economic situation in the country. Indices for particular economic activity measure the average change in the prices of industrial products, which are produced and sold by Bulgarian enterprises. This is done on the bases of constant sample of groups of products, produced by the activity and sold on the domestic market or directly exported on the non-domestic market and that sample is representative for total industrial production.
The sources of information are two monthly surveys:
Survey on ‘Producer price indices on domestic market’;
Survey on ‘Producer price indices on non-domestic market’.
11 June 2024
The Producer Price Indices measure the monthly change in prices of industrial products produced by Bulgarian enterprises and sold on the domestic market or on non-domestic market. The producer price is the ex-factory price and it includes discounts and other reductions. Excise duties and VAT are excluded. In most cases prices correspond to the prices stated at the moment of the contract. Each specific product is precisely described when first selected and is very carefully identified each month when its price is reported. The products are specified with all price-determining characteristics: (brand, content, material used, nature of the customer). When taking into account discounts, reporting units are asked to specify also the quantity, in order not to have fluctuations due to changes in customer's prices. The producer price indices measure the average of the actual prices received for a fixed basket of products that remains the same from one month to the next and also it attempts to take account of changes in quality by means of price changes. The surveyed prices take account of changes in quality that can be caused by a change in either the physical characteristics of a product or a change in the transaction characteristics.
Prices have to be reported on a fixed date around the 15th day of the reference month.
Legal unit (considered as enterprise) is both a reporting and observation unit.
The frame for identifying observation units for the population is the PRODCOM survey, which covers exhaustively all non-financial enterprises manufacturing industrial commodities and/or rendering industrial services with a specified threshold of receipts from sales of industrial production and industrial services. The sample model ensures 90% coverage of sold production in terms of value at the national level for each NACE Rev.2 class.
The number of units in the population of interest (PRODCOM survey) encompasses about 29 000 units.
All regions of Bulgaria are covered.
The 15th day of each month.
PPI (domestic and non-domestic market) satisfies the principle of accuracy as it describes development of producer prices.
The data are generally considered to be final at first released, there are no estimates produced or published and PPIs are not subject to revision.
Sampling error is not measured due to complexity of price indices and due to the use of non-probability sampling.
There were negligible non-sampling errors concerning coverage, measurement and processing errors. Most of measurement errors are detected and corrected through the logical and arithmetical controls of the Information system “Business cycles” (Online Information system for data collection, editing and processing of the STS information).
Response rate is near to 100%. In most of the cases missing prices are replaced using relevant techniques.
Indices (%)
Treatment of missing prices:
Prices for temporarily missing products are handled by one of following methods: (1) asking the enterprise to estimate the missing price, (2) imputing the missing price by the price change for the prices that are available from the same enterprise from the same PRODCOM group (3) imputing the missing price by the price change for a particular comparable product from similar enterprise, (4) imputing the missing price by the price change for the prices that are available in the elementary aggregates, or (5) repeating the last reported price.
When a specific product subject to price monitoring, stop producing, is replaced with a new product from the same product group, which will replace approximately the oldest product on the market. The replacement of specifications basely is made through the chain of elementary indices of the old and of the replaced products.
Adjustment for seasonal products: When selecting the product samples, it is ensured that there are some price data available for each month of the year. This is achieved through working closely with respondents. When the price for a particular seasonal specification is not available, an imputation is made using the short-term price change from a matched sample of specifications from the same product group or enterprise.
The type of index used is a Laspeyres index.
Calculation of the producer price indices on domestic and on non-domestic market
Producer price indices are base weighted (Laspeyres) indices - that is to say they are weighted according to the turnover in the base year, currently 2021. After specification’s price collection from the enterprises, elementary indices (price relatives) are calculated for each specification (price relative – specification price in the current month divided by average price of that specification in the base year). After that price relatives are weighted with sales structure in the base year.
Producer price indices at different levels of aggregation are calculated from successive aggregations in which each level of aggregation uses the arithmetic mean of indices at the level below, duly weighted with sales structure in the base year following the structure of the NACE.Rev.2.
In the weighting system, there are two categories of weights, which depend on the level of aggregation:
At group level – 3-th digit of NACE.BG-2008 indices are calculated as price relatives are weighted with sales structure on the domestic or on the non-domestic market by PRODCOM groups. These weights are received from annual PRODCOM survey in the base year.
Producer price index calculation at higher levels of aggregation is base weighted Laspeyres indices that is to say they are weighted according to the turnover structure on the domestic and on non-domestic market in the base year.
Calculation of Total Producer Price Index
Total producer price index is calculated from Producer price index on the domestic market and Producer price index on the non-domestic market weighted with the turnover structure on domestic and on non-domestic market to the total value of turnover at each level of aggregation.
Information for calculation of Producer price indices in industry is received on the bases of two monthly surveys on producer prices of industrial products, sold on domestic market and on industrial products sold on non-domestic market. The aim of Producer price surveys is: (1) To compare prices of specific products with equal quality in the two surveyed time periods; (2) In the case of quality change of the surveyed specific products this quality change to be taken into account.
Data collection is based on a representative sample of products.
According to the methodology the sampling method used for domestic producer price index compilation involves a three stage sampling process: first PRODCOM groups are selected, as a second step - reporting units are selected and then specific products (transactions) are selected. The sample method used is probability proportional to size.
Producer price indices on domestic market. The sampling method used involves a three stage sampling process: first PRODCOM groups, second reporting units and then specific products (transactions) are sampled.
The sample of product groups is based on the annual survey of production and sales of industrial products - the PRODCOM survey. A sample of reporting is made for each of the selected PRODCOM groups. These units (enterprises) will participate in the price survey. A probabilistic method - proportional to the size is used to ensure sufficient coverage. The number of the units selected in the sample depends on the degree of industrial concentration of the enterprises from each sampled PRODCOM group.
For each enterprise with the corresponding PRODCOM group that was sampled for price survey, the Price index estimation is based on the sample of specific product (specifications). For each enterprise the selected PRODCOM product groups are desegregated into group of product that show equal price changes and from these groups representative specification (specific products) are selected. The selected specifications reflect in the best way the price changes of the whole group. At that stage of sampling so called ‘purposive sampling’ or ‘expert choice’ is applied. The experts from the selected enterprises choose the price quotations, in other words products with the highest sales volume are selected and long presence on the market.
Producer Price Indices on Non-domestic Market. The sampling technique applied has two stages – sample of enterprises, and sample of representative products/transactions.
The sample of enterprises is made on the bases of annual information on receipts of export sales of industrial enterprises. Enterprises with significant amount of export sales are selected for price survey.
The basic concepts relating to determination of priced products relating to export prices are the same as those applying to domestic prices.
For Domestic producer prices survey the sample includes 1600 industrial enterprises 920 PRODCOM groups and 7000 specific products (specifications).
For Non-domestic producer prices survey the sample includes 630 industrial enterprises (direct exporters of industrial products) 550 PRODCOM groups and 2500 specific products (specifications).
Monthly
The Producer price indices (Total PPI, PPI on domestic market and PPI on non-domestic market) are released 30 days after the end of the reference month according to the Release calendar posted on the NSI website.
Producer price indices in industry are representative for the whole country; they are not representative for the regions of the country.
To calculate the producer price indices on the domestic and on the non-domestic market NSI applies methodology, which is in line with the international standards.
The monthly indices are presented as time series. Indices are fully comparable over time.
