ESS Standard for Quality Reports Structure (ESQRS)
National Statistical Institute of Bulgaria
|Contact organisation unit|
Consumer Prices, Housing prices and PPP Department
|Contact person function|
|Contact mail address|
2 Panayot Volov Str., 1038 Sofia
|Contact email address|
|Contact phone number|
+359 2 9857 181
|Contact fax number|
The House Price Indices (HPI) are quarterly indicators that measure the changes in the dwellings transaction prices that households acquire on the market (both newly built and already existing). The data are based on harmonised definitions and concepts included in the Regulation (EU) 2016/792 of the European Parliament and of the Council, Commissin Implementing Regulation (EU) 2020/1148 and described in the OOH Technical Manual.
The HPI are indicators comprising two sub-indices:
• HPI of new dwellings (newly built);
• HPI of existing dwellings (trade between households).
The HPI emphasize on the market price of dwellings, so non-marketed prices are ruled out from the scope of the HPI (self-builders are excluded). All transactions are included (both cash and mortgage) acquired by households regardless of its final use, so dwellings bought by households for uses other than owner- occupancy are included (for investment, e.g. to rent it out).
Since 2022, this index cover purchases of apartments and houses. Until end of 2021, purchases of houses were excluded due to their insignificant number of transactions.
Luxury properties are out of the scope of HPI.
HPI are constructed and produceed according to Regulation (EU) 2016/792 on harmonised indices of consumer prices and the house price index and the Commission Implementing Regulation (EU) 2020/1148 laying down the methodological and technical specifications in accordance with Regulation (EU) 2016/792 of the European Parliament and of the Council as regards harmonised indices of consumer prices and the house price index.
National HPI series are published according to the following categories:
H.1. Purchases of dwellings
H.1.1. Purchases of new dwellings
H.1.2. Purchases of existing dwellings
Regional HPI series are published for the following levels:
- statistical zones according Classification of Territorial Units for Statistics in Bulgaria (NUTS1)
- statistical regions according Classification of Territorial Units for Statistics in Bulgaria (NUTS2)
- for the six cities with population more than 120 000 inhabitants.
ESA 95 sector S. 14 (Household sector). HPI cover residential properties purchased by households in the reference period irrespective of the type of area in which they live, their position in the income distribution and their nationality status.
|Statistical concepts and definitions|
Index figures for the purchase of new and existing dwellings are compiled on the basis of full transaction prices, which since 2022 are collected through the use of an administrative data source. Transaction prices include the value of land.
The HPI are chain-linked Laspeyres-type indices.
The weights for the two sub-indices represent the total value of dwelling transactions for new and existing dwellings, respectively.
The administrative data source contain all the transactions.
The published data are as follows:
1) House price indices (HPI) by type of purchased dwellings (new/existing/total HPI), national level
• HPI, national level, 2015 = 100
• HPI, national level, previous quarter = 100
• HPI, national level, corresponding quarter of the previous year = 100
2) House price indices (HPI), by type of purchased dwellings (new/existing/total HPI), regional level
• HPI, by statistical regions, 2015 = 100
• HPI, by statistical regions, previous quarter = 100
• HPI, by statistical regions, corresponding quarter of the previous year = 100
• HPI, for the six cities with population more than 120 000 inhabitants, 2015 = 100
• HPI, for the six cities with population more than 120 000 inhabitants, previous quarter = 100
• HPI, for the six cities with population more than 120 000 inhabitants, corresponding quarter of the previous year = 100
Market price of a dwelling purchased by a private household.
Any published index or rate of change refers to the households' expenditures for the acquisition of residential property on the territory of Bulgaria.
The statistical population consists of households' expenditures spent for the acquisition of residential property on the economic territory of the country. Household sector covered in HPI includes all persons or groups of persons irrespective of the type of area in which they live, their position in the income distribution and their nationality status.
HPI covers all monetary transactions of residential properties (new and existing apartments) on the territory of the country, purchased by private domestic and nondomestic households (i.e.'domestic concept).
HPI cover the territory of the Republic of Bulgaria.
HPI are available at very detailed level but due to the limited number of transactions data are representative by the 6 statistical regions (NUTS level 2) and for the six cities with population over 120 000 inhabitants. .
• national level - quarterly data are available since Q1 2005;
• regional level - quarterly data are available since Q1 2015.
Since 2022 HPI compilation is derived from two different administrative data sources - the Property register (PR), maintained by the Registry Agency, in combination with data from the Cadastral Administrative-Information System (CAIS) by the Geodesy, cartography and cadaster Agency.
Until the end of 2021 the data source for compilation of HPI was a quarterly sampled survey “House price indices“ that gave information on the market prices of the dwellings and on the major price determining characteristics. The sample covered enterprises with real estate activities (68.31 -NACE rev.2) and residential construction enterprises or enterprises with investments in residential buildings.
The use Property Register combined with the Cadastral Administrative-Information System (CAIS) are considered as the most adequate approach for derivation of HPI weights.
|Frequency of data collection|
Since 2022, the compilation of weights and prices for HPI and the value and number of transactions for HSI, is based on the combined information from the PR and CAIS data.
PR data are collected monthly trough a web application for automated secure connection between NSI and the Registry Agency.
Records from PR provide information about the on transactions’ value and also includes:
- the date of registration,
- the role of the parties (individuals or legal entity),
- the type of the registration act,
- total material interest of a transaction,
- the registry tax,
- Real estate property description, including:
- type of the property (land, a building or a single property in a building),
- area in square meters,
- the address (for part of the properties),
- cadastral number (for part of the properties),
Cadastral data are provided quarterly, in txt files, using a safe data transmission channel.
Records contain information about:
- type of the property (a plot, a building or a single property in a building);
- type of the properties’ ownership (private, by state, by municipality, etc.);
- area in square meters;
- type of the territory (urban, agricultural, forest, etc.)
- usage type of land;
- functional type of the building;
- functional type of the single property in building;
- number of building’s floors.
The PR and CAIS data are merged using a property (cadastral) identification number as a key variable.
Until the end of 2021 data collection was based on an information system on the site of NSI - IS Prices of dwellings, where firms had the possibility to report transactions online and in real time, including information on dwellings’ prices, the characteristics of the transacted properties, location, time of transaction, etc.
Validations include rules for automatic quality controls of prices and property’s area. They are done on two stages:
• annually - the price limits (minimum and maximum price level) in each strata are calculated based on the transactions from the previous year;
• quarterly - automatic check control are carried including determination of:
- extreme values of prices by strata;
- extreme values of area - below 20 sq.m. and above 250 sq.m (for apartments) or above 350 sq.m. (for single-family house).
Extreme values are identified and eliminated.
Variables available in both registers passes through pre-defined validation rules during the merging process in order to investigate and remove incorrect interpretation of properties’ characteristics.
Bulgarian HPI cover transactions of apartments and houses. Untill the end of 2021 purchases of houses were excluded due to their insignificant number of transactions collected with the quarterly sampled survey “House price indices“.
HPI are calculated as a chain-linked Laspeyres type price index. Indices are constructed both on national and on regional level using stratification combined with hedonic method to take into account the quality changes.
Stratification is based on:
• the type of purchased dwellings (new/existing dwellings),
• geographical area (defined at district level).
The quarterly compilation involves the following basic steps:
• Identification of individual residential transactions;
• Calculation of the price per square meter for each residential property;
• Estimation of the hedonic regression models and derivation of the pure price change for each strata;
• Aggregation to the upper levels using Lasspeyres formula.
The following aggregation levels are applied:
• level 1 - newly built and existing dwellings;
• level 2 - locality by NUTS level 2 (statistical regions);
• level 3 - locality by NUTS level 3 (districts);
Properties are categorized by type of a dwelling (flats, houses).
In the regression model the dependant variable is a logarithm of the price, the regression factors are: locality, property’s area, land area, type of dwelling and type of settlement (“district’s main city”, “towns and rural”, “resorts”).
Hedonic function is estimated in the beginning of each year (t), through a regression model that uses the data of the previous year (t-1): estimated regression coefficients are kept constant for the whole reference year (t).
In order to guarantee a minimum amount of observations in each stratum, regression models are calculated for 28 districts at NUTS level 3 and also for 6 big cities with population above 120000 inhabitants.
Each aggregated index is calculated as a weighted arithmetic average of elementary indices.
HPI weights are updated each year and the weights for index calculation in year (t) reflect the average annual value of dwellings transaction calculated from the preceding three years (t-3), (t-2) and (t-1) and price updated to 4th quarter of year (t-1).
Each year indices are calculated using fourth quarter of the previous year=100 as base reference period and are rebased to 2015=100 using the chain linked method.
No seasonal or calendar adjustments are made.
A combination of detailed stratification and hedonics is applied to adjust the quality changes in the prices of the dwellings, as described in point Data compilation.
All data are checked for completeness and consistency with statistical concepts and definitions. HPI are produced in compliance with HPI methodological requirements of the Owner-Occupied Technical Manual.
The quality of the HPI are routinely reviewed using a framework that is based on the OOH technical manual and the European Statistical System (ESS) definition of quality.
Data on the house price indices are used for analysis, prognoses and management purposes by the government institutions, agencies and other organizations.
The main national users are: BNB, Ministries, National and State Agencies; information media;
Major international user are : Eurostat, ECB, IMF, UN ECE.
No missing data. BNSI produces and delivers the full set of HPI indices and weights.
|Data completeness - rate|
|Accuracy and reliability|
Overall accuracy is not estimated.
The accuracy of source data is monitored by assessing the methodological soundness of price and weight sources and the adherence to the methodological recommendations.
Since 2022 HPI are based on an administrative data source, which covers all market transactions.
|Sampling errors - indicators|
Non-sampling errors are not quantified for the HPl. NSI tries to reduce non-sampling errors through continuous methodological improvements and validation methods which help us to avoid coding and typing errors.
|Over-coverage - rate|
|Common units - proportion|
|Non response error|
|Unit non-response - rate|
|Item non-response - rate|
|Imputation - rate|
|Model assumption error|
|Data revision - policy|
HPI are revisable under the terms of Commission Regulation (EC) No 1921/2001 of 28 September 2001. Published HPI may be revised for mistakes, new or improved information and methodological improvements.
|Data revision - practice|
HPI are published as preliminary and are usually confirmed or revised in the following quarter.
|Data revision - average size|
|Timeliness and punctuality|
Data are published according to NSI Release calendar - 85 days after the end of the reference quarter.
|Time lag - first results|
HPI are final when first published.
|Time lag - final results|
HPI are published 85 days after the end of the reference quarter.
Data are always delivered and published on the pre-announced release dates.
|Punctuality - delivery and publication|
|Coherence and comparability|
|Comparability - geographical|
HPI data are calculated on both national and regional levels. The regional data are fully comparable with one another.
HPI are based on harmonised definitions and classifications set by series of legal acts. Therefore, the indices can be considered to be comparable to the other EU Member States HPIs.
|Asymmetry for mirror flows statistics - coefficient|
|Comparability - over time|
In principle HPI are comparable over time. Nevertheless, from the first construction of HPI till now, the methodology has constantly developed and improved and therefore some breaks in time series must be considered:
• data for 2005 - 2008 is based on estimates;
• data for 2009 - 2014 are preliminary HPI and the data sources for indices construction are: (1) quarterly pilot survey of newly built dwellings' prices and (2) quarterly survey "Market prices of dwellings" carried out by NSI between 1993 - 2014;
• since 2015 NSI has started regular production of HPI for new and existing dwellings according to a harmonised methodology and coverage in compliance with Commission Regulation (EU) 2016/792 of the EP and of the Council and with the Commission Implementing Regulation (EU) 2020/1148.
• since Q1 2022 BNSI has replaced the sampled survey with a more complete administrative data source for production of HPI for new and for existing dwellings, therefore breaks in time series must be considered in Q1 2022.
|Length of comparable time series|
Since 2015'Q1 until 2021'Q4 - 28 quarters.
|Coherence - cross domain|
Only one HPI set is available.
|Coherence - sub annual and annual statistics|
Annual HPI are derived from the quarterly indices and are fully reconcilable.
|Coherence - National Accounts|
|Coherence - internal|
HPI are internally coherent. Higher level aggregations are derived from detailed indices in accordance with strictly-defined procedures.
|Accessibility and clarity|
Electronic publication 'Key indicators for Bulgaria', 'Statistical Yearbook of the Republic of Bulgaria’.
HPI are available to all users on the NSI website under the heading Housing price statistics: https://www.nsi.bg/en/node/13023
|Data tables - consultations|
Microdata are not diseminated.
|Metadata - consultations|
|Documentation on methodology|
EU and EC regulations:
|Metadata completeness – rate|
Quality report in ESS Standard for Quality Reports Structure (ESQRS) - https://www.nsi.bg/en/content/15357/метаданни/house-price-index-hpi
|Cost and burden|
|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|
lndividual data are not published in accordance with article 25 of the Law on Statistics. The publishing of individual data can be performed only in accordance with article 26 of the same law.