National Statistical Institute of Bulgaria

Consumer prices, Housing prices and PPP Department

2 Panayot Volov Str.

1038 Sofia

Bulgaria

The House Price Indices (HPI) is quarterly indicator that measures the changes in the transaction prices of dwellings purchased by households. They are calculated according to a harmonised approach and a single set of definitions.

The HPI is comprising two sub-indices:

• HPI of new dwellings (newly built);
• HPI of existing dwellings (trade between households).

The HPI emphasizes 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). Price include land value. Luxury properties are out of the scope of HPI.

The HPI is broken down into the following expenditure categories:

• H.1. Purchases of dwellings
• H.1.1. Purchases of newly built dwellings
• H.1.2. Purchases of existing dwellings

ESA 2010 sector S. 14 (Household sector).

Both HPl and HSI 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.

The main statistical variables are price indices.

The basic unit of statistical observation are transaction prices of dwellings purchased by households.

Transaction prices include the value of land.

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 and in HSI 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.

Both, HPI and HSI, cover all monetary transactions of residential properties (new and existing apartments) on the economic territory of the country, purchased by private domestic and nondomestic households.

Bulgaria has no overseas territories. The economic territory of Bulgaria consists of the geographic territory. The HPI and HSI cover the entire economic territory consistent with NA. No parts of the economic territory of Bulgaria are excluded from the index.

HPI are available at very detailed level but due to the limited number of transactions data are representative at NUTS level 2 and for the 6 cities with population over 120000 inhabitants.

HPIs:

• national level - quarterly data are available since Q1 2005;
• regional level - quarterly data are available since Q1 2015.

HSIs:

• national level, value of transactions - annual data are available since 2010;
• national level, value of transactions - quarterly data are available since Q1 2016;
• national level, number of transactions in dwellings - quarterly data are available since Q1 2016;
• regional level, value of transactions - quarterly data are available since Q1 2022;
• regional level, number of transactions in dwellings - quarterly data are available since Q1 2022.

2015=100.

The following units are used:

• Index point;
• Percentage change on the same period of the previous year (rates);
• Percentage change on the previous period (rates);
• Percentage share of the total (weights);
• Percentage in the year (the share of the quarter from the annual value or number of transactions).

HPI is a quarterly statistics.

EU legal acts:

• The basic act providing for the compilation of the HPI is the European Parliament and Council Regulation (EU) 2016/792, of 11 May 2016 on harmonised indices of consumer prices and the house price index, and repealing Council Regulation (EC) No 2494/95.
• The relevant implementing act is the Commission Implementing Regulation (EU) 2023/1470 of 17 July 2023 laying down the methodological and technical specifications in accordance with Regulation (EU) 2016/792 of the European Parliament and of the Council as regards the house price index and the owner-occupied housing price index, and amending Commission Regulation (EU) 2020/1148.

All relevant regulations as well as further methodological details can be found in the Housing Price Statistics section on Eurostat’s website under => Legislation.

Bulgarian legal acts and other agreements:

• Law on Statistics (Statistics Act);
• Annual National Statistical Programme;
• Strategy for Development of the National Statistical System, 2021 - 2027.

Not applicable for HPI.

Regulation (EC) No 223/2009 of the European Parliament and of the Council, of 11 March 2009, on the transmission of data subject to statistical confidentiality to the Statistical Office of the European Communities;

Statistics Act | National statistical institute (nsi.bg)

The confidentiality of the HPI data set is treated in respect of national legislation: Law of Statistics, Chapter 6 ‘Protection of secrecy’, Articles 25, 26, 26a, 27 and 27a. Art. 25 stipulates that individual data (‘individual data’ are data about a specific statistical unit) received and collected through statistical surveys shall constitute a statistical secret and may be used only for statistical purposes. Individual data received for the purposes of statistical surveys may not be used as evidence before the bodies of the executive and the judiciary.

The NSI and statistical authorities and their staff may not disclose or provide:

• individual statistical data;
• statistical data, which can be matched in a way that enables the identification of a specific statistical unit;
• 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 per cent of the total value of such parameter for all units in the population.

The individual data may be provided only if:

• it is transferred to Eurostat where this is necessary for development and production of European statistical information;
• it is provided to the National Statistical Institute by statistical authorities where this is necessary for development and production of official statistical information;
• the subject to which such data relate has granted consent therefor.

Individual anonymous data is provided for the purposes of scientific research to higher schools or legal entities, whose main activity is scientific research, with a permission of the Chairperson of the National Statistical Institute.

According to the Law of statistics the receipt, processing, usage and storage of statistical data representing statistical secret is carried out in a procedure set out in a regulation endorsed by the President of the National Statistical Institute.

The Section 3 of the Rules for Dissemination of Statistical Products and Services endorsed by the President of the NSI regulate the protection of secrecy of individual data.

The Rules for Provision of Anonymised Individual Data for Scientific and Research Purposes endorsed by the President of the NSI regulate the relations in terms of provision of anonymised individual data by the NSI for scientific and research purposes and the order of their  receipt by the users.

Rules for Provision of Anonymised Individual Data for Scientific and Research Purposes | National statistical institute (nsi.bg)

Data are treated in respect of national legislation: Individual 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.

Statistics Act | National statistical institute (nsi.bg)

Specific rules for treating the data set with regard to statistical confidentiality are applied according to the Rules for Provision of Anonymised Individual Data for Scientific and Research Purposes endorsed by the President of the NSI.

Rules for Provision of Anonymised Individual Data for Scientific and Research Purposes | National statistical institute (nsi.bg)

In case of data anonymization the following requirements are applied:

• Anonymised data are separate statistical records which have been amended according to the best existing practices in order to reduce the risk of direct or indirect identification of the statistical units to which they refer
• Additional data processing means deletion of names, addresses, identification numbers and all of the characteristics that might lead to a risk of disclosure and misuse of individual records in the databases with individual data. Measures such as suppression of geographical details, age, place of birth, occupation, economic activity, type of ownership, etc. that can be taken in order to ensure that the identification of individuals and economic entities shall be impossible.
• Anonymised individual data cannot be provided if it is in conflict with the provisions of art. 25 of the Statistics Act;
• The individual records in the databases of the requested survey shall be processed by competent employees as all identifying individual attributes (name, address, publicly accessible identification number etc.) which directly or indirectly a given statistical unit can be identified shall be deleted from the data through.
• In case of records in which some of the characteristics do not fulfilled these rules, the directorates responsible for the preparation of the data shall decide whether they should be completely deleted or to delete the data only in the cells of these characteristics or to take other appropriate solutions for protection of individual data.

The release of the Bulgarian HPI/HSI follows a preannounced official Release Calendar presenting the results of the statistical surveys carried out by the National Statistical Institute.

The Release Calendar is publicly accessible on NSI’s website.

The calendar is available on the NSI website:

Release Calendar | National statistical institute (nsi.bg)

HPI and HSI are published on the NSI website in section Housing price statistics 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.

Quarterly (HPI and HSI) and annually (weights)

Not available.

HPI and HSI table data are available on NSI’s website, theme Housing price statistics: Housing price statistics | National statistical institute (nsi.bg)

HPI data are also published in the following regular NSI publications in printed and/or electronic format:

• Key indicators for Bulgaria – quarterly, electronic publication: Key Indicators for Bulgaria (as of 03.07.2023) | National statistical institute (nsi.bg);
• Statistical Yearbook – annual, printed edition and electronic edition on CD-ROM.

On-line database on NSI’s website, Information System INFOSTAT:

https://infostat.nsi.bg/infostat/pages/module.jsf?x_2=186

In principle, there is no access to microdata. The microdata, as long as it is not confidential, could be provided to users on request without a breach of the confidentiality principle.

Not relevant.

The HPI metadata is available on NSI’s website: House price index (HPI) | National statistical institute (nsi.bg)

The HSI metadata is available on NSI’s website: House sales indicators (HSI) | National statistical institute (nsi.bg)

The HPI Quality Reports is available on NSI’s internet site: House price index (HPI) | National statistical institute (nsi.bg)

The HSI Quality Reports is available on NSI’s internet site: House sales indicators (HSI) | National statistical institute (nsi.bg)

The quality activities in Bulgarian National Statistical System (NSS) are built on the fifteen principles of the European Statistics Code of Practice (https://ec.europa.eu/eurostat/web/quality/european-quality-standards/european-statistics-code-of-practice), covering the institutional environment, statistical processes and statistical outputs. The NSS Quality Assurance Framework includes methods and tools that aim to guarantee the compliance with the requirements to the statistical processes and products, and to ensure the required statistical information quality. A formal quality assurance framework is not yet implemented for the HPI.

One of the main tasks of Consumer Prices, Housing prices and PPP Department is to control all processes, related to the HPI/HSI production with respect to the quality of the index results. The following processes are covered by that task:

• Data processing (e.g. data entry, data editing);
• Index computation (i.e. mathematical formulae);
• Personnel training;
• Monitoring of the implementation of HPI/HSI production.

Data are checked for completeness and consistency with statistical concepts and definitions. Automatic quality controls have been implemented within the HPI production process, in order to detect and correct errors in the data files that are received. Outliers, such as dwellings with particularly small or large floor area or very high or low prices per m2 etc. are excluded from the index.

The HPI/HSI Quality Reports following the ESS Standard for Quality Reports Structure (ESQRS) are produced and are updated each year.

The HPI Quality Reports is available on NSI’s internet site: House price index (HPI) | National statistical institute (nsi.bg)

The HSI Quality Reports is available on NSI’s internet site: House sales indicators (HSI) | National statistical institute (nsi.bg)

The main national users could be classified as follows:

• National state institutions: National Assembly of The Republic of Bulgaria, the Government, Bulgarian National Bank, national and state agencies. That group of users is considered as most important.
• Other national users: municipal authorities, research communities, students, business communities, media, etc.
• Internal users: other statistical divisions in the NSI.

HPI/HSI outcomes are mainly used as input to economic forecasting and analysis, for management purposes, deflating other series, etc.

The main international usersare ECB, IMF, UN ECE.

NSI conducts an annual online statistical survey "Users' satisfaction" which covers all statistical domains. It aims to assess user satisfaction in NSI data provision and to outline the recommendations for future development of statistical system according to the needs of the users.

Analysis of the last survey conducted in 2022 are available on the following link: User satisfaction

No missing data. Bulgaria produces and delivers the full set of HPI indices and weights.

Statistical data are with good accuracy. The accuracy of HPI is assured by strictly following Eurostat's methodological recommendations and regulations.

The data collection covers the whole universe of transactions. The HPI uses the real transaction prices registered in Property Register of Registry Agency. Nonetheless, even transaction prices (as recorded in the Property Register, for instance) may, in some cases, be subject to bias (underreporting). NSI is eliminating the underreporting of prices by annual determination of minimum and maximum price levels by strata, and excluding from calculations transactions bellow and over the limits.

Not relevant. The HPI is based on an administrative data source, which covers all market transactions.

Non-sampling errors are not quantified for the HPI. The NSI tries to reduce non-sampling errors through continuous methodological improvements and validation methods that can help us to avoid coding and typing errors.

The time lag between the end of the quarter to which the HPIs/HSIs relate and their national publication is usually 82-85 calendar days.

Data are sent according to Regulation 2016/792: 85 days after the end of the reference period (indexes) and no later than June 15^th of the year following the reference year (weights).

HPI and HSI are calculated on both national and regional levels. The regional data are comparable across NUTS level 1 and level 2 regions and across the 6 big cities with population above 120000 inhabitants.

In principle HPI are comparable over time. Nevertheless, from the first construction of HPI until now, the methodology has constantly developed and improved and therefore some breaks in time series must be considered:

• data for 2005-2008 are based on estimates;
• data for 2009-2014 are provisional HPI and the data sources for the 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 Regulation (EU) 2016/792 of the European Parliament and of the Council and the Commissin Implementing Regulation (EU) 2020/1148;
• since 2022, NSI 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 should be considered in first quarter of 2022.

The HSI are comparable over time.

Not applicable. There is only one set of HPIs is available and there is only one set of HSIs is available.

The OOHPI partly overlaps the scope of the HPI. However, both indexes cover a different set of transactions and any comparison of the two indices should be done with this in mind.

HPI are internally coherent. Higher level aggregations are derived from detailed indices in accordance with strictly defined procedures.

According to the budget estimates of the National Statistical Programme for 2022, the total cost of HPI, HSI and OOHPI production is 778.408 thousand euros.

The HPI series, including back data, is revisable under the terms set in Articles 27-29 of Commission Implementing Regulation (EU) 2023/1470.

No revisions to report.

See below.

The HPI (both for newly built dwellings and for existing dwellings) is compiled using the administrative sources:

• Property register (PR), maintained by the Registry Agency; and
• Cadastral Administrative-Information System (CAIS) by the Geodesy, cartography and cadastre Agency.

The Property Register (PR) data combined with the Cadastral Administrative-Information System (CAIS) are the sources that are used for derivation of HPI weights.

HSI are based on the value and number of transactions from the Property Register (PR) dataset.

Quarterly.

Property Register (PR), maintained by the Registry Agency (RA)

PR data are collected monthly trough a web application for automated secure connection between NSI and the Registry Agency.

Cadastral Administrative-Information System (CAIS) by the Geodesy, Cartography and Cadastre Agency

Cadastral data are provided quarterly, in txt-files, using a safe data transmission channel.

HPI validation

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.

See below.

See below.

HPI is a Laspeyres-type price index.

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 stratum;
• Aggregation to the upper levels using Laspeyres formula.

The following aggregation levels are applied:

• level 1 - newly built and existing dwellings;
• level 2 - locality by NUTS level 1 (statistical zones);
• level 3 - locality by NUTS level 2 (statistical regions);
• level 4 - locality by NUTS level 3 (districts);
• level 5 - locality by stratum (district centre, towns and rural, resorts).

HPI sub-indices and elementary aggregates weights are based on data on household expenditure on transacted dwellings.

HPI weights for index calculations in year (t) reflect the average annual value of dwellings transaction calculated from the preceding three years: (t-3), (t-2) and (t-1), price updated to the fourth quarter of (t-1).

HPI weights are updated annually.

HPI weights are updated each year and weights for index calculations in year (t) reflect the average annual value of dwellings transaction calculated from the preceding three years: (t-3), (t-2) and (t-1), price updated to the fourth quarter of (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.

Both for newly built dwellings and for existing dwellings the hedonic method is applied.

The average characteristics method is used for HPI calculation.

In principle, the hedonic function is estimated for each stratum district centre, towns and rural, resorts. Where the available number of transacted dwellings is insufficient to enable the estimation of the hedonic model for a certain stratum then the hedonic function is estimated at the higher level for a district (NUTS level 3).

In the regression model for stratum “district centre” and for stratum “resorts” the dependant variable is a logarithm of the price, the independent variables are: property’s area, land area and type of dwelling.

In the regression model for stratum “towns and rural” the dependant variable is a logarithm of the price, the independent variables are: property’s area, land area, type of dwelling and locality (town/rural).

In the regression model for district (NUTS level 3) the dependant variable is a logarithm of the price, the regression factors are: property’s area, land area, type of dwelling and locality (“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).

The set of average characteristics is based on previous year data.

Not applicable.

Not applicable.

See below.

Transaction prices are recorded after the transfer of the ownership, when the legal act is entered into the Property Register.

VAT is included in the price of new dwellings.

Taxes other than VAT are not included in the price of dwellings.

Government subsidies are set up in the law on the settlement of the rights of citizens with multi-annual housing deposits. Deposits are derived from 'points', which are calculated by an initial amount of money placed on bank deposit by a citizen, and the number of years passed until a dwelling is purchased. In such cases dwelling are purchased at market prices and the deposit is refunded to the person after the transaction. Hence, those transactions are covered by HPI in full transaction price, and the subsidies are not reflected. Other form of subsidies are dwellings sold by municipalities to households in need. Prices are set up in the ordinance issued by each municipality. Those dwellings are treated as 'existing dwellings' new to households' sector' and are purchased on non-market prices, so they are out of the scope of HPI.

The price of land is included in both prices and weights.

Housing cooperatives are not covered in the HPI.

"Non-market" transactions are identified by the type of the registration act entered in the Property Register. "Non-market" transactions are excluded from HPI/HSI calculations.

The multi-object transactions are treated as one transaction if included properties belong to the same settlement.

The fractional transactions are treated as separate transaction.

The outliers are defined separately for newly built dwellings and for existing dwellings for each of the following stratum:

• for sales of apartments in:
  • district’s main city;
  • towns;
  • villages;
  • resorts.
• for house sales in:
  • district’s main city;
  • towns;
  • villages;
  • resorts.

The outliers’ calculation passes through the following steps:

a) calculation of natural logarithm (ln) of price per square meter;

b) definition of the lower (25%) and upper (75%) percentiles of the logarithm;

c) calculation of IQR (interquartile range) - difference between upper (Q3) and lower percentile (Q1);

d) calculation of SQR (semi-quartile range) - difference between upper (Q3) and lower percentile (Q1), divided by 2;

e) calculation of minimum and maximum value:

• minimum value: Percentile 25% - 1.5*IQR
• maximum value: Percentile 75% + 1.5*IQR

f) calculation of the minimum and maximum price threshold per square meter from the value calculated in the above point according to the formula: EXP (value) from the minimum and maximum values calculated in the above point by strata.

The outliers are updated each year based on the previous year's data.

The identified outliers are excluded from the HPI calculations.

Not relevant.

No seasonal adjustment is made.

None.