Owner-occupied housing price index (OOHPI)

Metadata

Owner occupied housing price index (OOHPI)
Contact
Contact organisation	National Statistical Institute
Contact organisation unit	Consumer Prices, Housing prices and PPP Department
Contact name	Albena Dancheva
Contact person function	Head of Department
Contact mail address	2 Panayot Volov Str., 1038 Sofia
Contact email address	adancheva@nsi.bg
Contact phone number	+359 2 9857 767
Contact fax number
Metadata update
Metadata last certified	24 June 2024
Metadata last posted	24 June 2024
Metadata last update	24 June 2024
Statistical presentation
Data description	The Owner occupied housing price index (OOHPI) is a quarterly indicator that measures the evolution of the transaction prices of dwellings purchased by owner-occupiers, the changes in the expenditures connected with the acquisition of dwellings, and the cost of other goods and services that households acquire in their role as owners of dwellings. All prices are measured using the net acquisition approach. Under this approach, prices are measured to reflect the change in the cost of goods and services which are new to the hosuehold sector as a whole. Sales between the households are out of the scope of the OOHPI. Indices are based on harmonised definitions and concepts according the Regulation (EU) 2016/792 of the European Parliament and of the Council, Commissin Implementing Regulation (EU) 2023/1470 and described in the OOH Technical Manual.
Classification system	According the Commission Implementing Regulation (EU) 2023/1470 laying down the methodological and technical specifications as regards harmonised indices of consumer prices and the house price index, the classification system for OOHPI includes the following categories: O.1. Owner-occupiers’ housing expenditures O.1.1. Acquisitions of dwellings O.1.1.1. New dwellings O.1.1.1.1. Purchases of new dwellings O.1.1.1.2. Self-build dwellings and major renovations (not observed yet) O.1.1.2. Existing dwellings new to households (not observed yet) O.1.1.3. Other services related to the acquisition of dwellings O.1.2. Ownership of dwellings O.1.2.1. Major repairs and maintenance O.1.2.2. Insurance connected with dwellings (observed until q4’2021) O.1.2.3. Other services related to ownership of dwellings (observed since q1’2015).
Sector coverage	Hoseholds on the territory of the country, which are owner-occupiers, irrespective of the type of area in which they live, their position in the income distribution and their nationality status.
Statistical concepts and definitions	OOHPI compilation follows methodological standards set out in the Technical Manual on Owner-Occupied Housing (OOH) provided by Eurostat to ensure comparability of indices across Member States. Currently ‘Self-build dwelling and major renovations’ and ‘Existing dwellings new to the household sector’ are not calculated. Until achieving the full coverage of OOHPI the data are subject to revisions according to the Commission Implementing Regulation (EU) 2023/1470 of 17 July 2023. The published OOHPI includes the following sub-indices:: • O.1.1.1.1. Purchases of new dwellings: Index figures for the ‘Purchase of new dwellings’ are compiled on the basis of full transaction prices of newly build dwellings that households acquire on the residential market. 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. • O.1.1.3. Other services related to the acquisition of dwellings: The index for ‘Other services related to the acquisition of dwellings’ includes the following four sub-indices: - index of notary deeds; - index of real estate fees; - index of Registry Agency fees; and - index of municipality (local) taxes. • O.1.2.1. Major repairs and maintenance: The price index for ‘Major repairs and maintenance’ is compiled based on a number of pre-defined set of typical activities on major repair and maintenance obtained from enterprises, which execute constraction works on residential buildings. • O.1.2.2. Insurance connected with the dwellings: The index for ‘Insurance connected with the dwellings’ has been discontinued at the end of 2021 due to the low share in households’ expenditures. This sub-index considered the service charges paid by owner occupiers for the kinds of insurance for the structure of his dwelling (e.g.: walls, fences, gates, etc). • O.1.2.3. Other services related to ownership of dwellings: Currently, ‘Other services related to ownership of dwellings’ includes the annual property tax payed to municipalities by each owner of a residential property. The OOHPI sub-indices are chain-linked Laspeyres type’s idices.
Statistical unit	Prices incurred by private households, which are owner-occupiers.
Statistical population	The statistical population consists of all households' expenditures spent for the acquisition of residential property new for the households’ sector and expenditures incurred by households in their role as an owner-occupier.
Reference area	OOHPI cover the whole territory of the country.
Time coverage	Data are available since 2015. Until the end of 2021 ‘Purchases of new dwellings’ index was calculated using sampled survey data. Since 2022 administrative data sources (the Property register complemented with Cadastral data) are introduced, therefore breaks in time series must be considered in Q1 2022.
Base period	2015=100
Unit of measure
The following units are used: • index • quarterly rate - percentage change compared to the previous quarter; • annual rate - percentage change compared to the same quarter of the previous year.
Reference period
Quarter
Institutional mandate
Legal acts and other agreements	• Regulation (EU) 2016/792 of the European Parliament and of the Council of 11 May 2016 on harmonised indices of consumer prices and the house price index, and repealing Council Regulation (EC) No 2494/95 • 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 harmonised indices of consumer prices and the house price index. • National Statistical Programme adopted annualy by Council of Ministers Decision.
Data sharing	None.
Confidentiality
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. http://www.nsi.bg/sites/default/files/files/pages/LegalBasis_e/Consolidated_version_of_amended_Regulation_223_2009_EN.pdf
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.
Release policy
Release calendar	OOHPI are published for the first time on the site of NSI in 2022 and will be released quarterly - 85 days after the end of the observed quarter. Date of publication of the statistical information is specified at the Release Calendar published on the site of the National Statistical Institute.
Release calendar access	The calendar is available on the NSI website: http://www.nsi.bg/en/node/480
User access	OOHPI 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.
Frequency of dissemination
Quarterly
Accessibility and clarity
News release	None.
Publications	None.
On-line database	OOHPI are available to all users on the NSI website under the heading Housing price statistics: http://www.nsi.bg/en/node/13023
Micro-data access	Microdata are not diseminated.
Other	None.
Documentation on methodology	EU and EC regulations: http://ec.europa.eu/eurostat/web/housing-price-statistics/legislation
Quality documentation	Quality report in ESS Standard for Quality Reports Structure (ESQRS) - https://www.nsi.bg/en/content/13025/housing-price-statistics
Quality management
Quality assurance	All data are checked for completeness and consistency with statistical concepts and definitions. OOHPI are produced in compliance with the methodological requirements of the Owner-Occupied Technical Manual. Automatic quality controls have been implemented within the production process in order to detect and correct errors. Outliers are excluded from calculations.
Quality assessment	The quality of the OOHPI is routinely reviewed using a framework that is based on the OOH technical manual and the European Statistical System (ESS) definition of quality.
Relevance
User needs	No information.
User satisfaction	None.
Completeness	OOH sub-indices 'O.1.1.2 Existing dwellings new to households' and 'O.1.1.1.2. Self-build dwellings and major renovations' are still excluded from OOHPI calculation. Since 2022 the sub-index for 'O.1.2.2 Insurance connected with dwellings' is not compiled due to the low share (under the treashold) in households' expenditures.
Accuracy and reliability
Overall accuracy	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. There is a variety of data sources both for weights (administrative data, statistical data from National Accounts, Construction Statistics, annual reporting of the enterprises, Statistics on Population and Housing fund Department, etc.) and prices (survey data, administrative data, construction companies, real estate agents, insurance companies, municipalities, etc.) for compilation of OOHPI sub-indices. In cases where surveys are used the type of survey and the price collection methods are designed to ensure sufficient coverage and timeliness.
Sampling error	Sampling errors are not calculated for OOHP indices.
Non-sampling error	Non-sampling errors are not quantified for the OOHPI. NSI tries to reduce non-sampling errors through continuous methodological improvements of data collection, validation and data management, which help us to avoid coding and typing errors.
Timeliness and punctuality
Timeliness	Data are published according to NSI Release calendar - 85 days after the end of the observed quarter.
Punctuality	Data are always delivered and published on the pre-announced release dates.
Coherence and comparability
Comparability - geographical	OOHP indices are only compiled on country level. Reagional indices are not available. However, OOHPI are developed according a common framework elaborated at European level and therefore, are commpareble across European countries.
Comparability - over time	Since first quarter of 2015 until fourth quarter of 2021 OOHPI are fully comparable over time. Due to transition towards administrative data source for calculation of “Purchase of new dwellings”, a break in time series must be considered in the first quarter of 2022.
Coherence - cross domain	OOHPI sub-indices are checked for coherence with the HPI sub-indices. Calculation of "Purchase of new dwellings" comprises the same number of transactions for both datasets but differ by the used weights. Weights for the compilation of OOHPI sub-index 'Purchase of new dwellings' are net of value of transactions from households to non-household’s sectors.
Coherence - internal	OOHPI are internally coherent. Higher level aggregations are derived from detailed indices in accordance with strictly-defined procedures.
Cost and burden
Data revision
Data revision - policy	OOHPI are revisable under the terms of Regulation (EU) 2016/792 of the European Parliament and of the Council, and Commission Implementing Regulation (EU) 2023/1470 of 17 July 2023. Published OOHPI may be revised for mistakes, new or improved information and methodological improvements.
Data revision - practice	OOHPI are published as preliminary and are usually confirmed or revised in the following quarter.
Statistical processing
Source data	Direct data sources in combination with administrative data are used for compiling OOHPI. OOH Prices • O.1.1.1.1. Purchases of new dwellings: Since 2022 the Property register (PR), maintained by the Registry Agency, in combination with data from the Cadastral Information System (by the Geodesy, cartography and cadaster Agency) are used as data sources for compilation of this sub-index. Until the end of 2021 the data source for compilation of this sub-index is a quarterly survey - 'Survey on the house price indices' that gives information on the market prices of the transacted 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. • O.1.1.3. Other services related to the acquisition of dwellings: “Index of notary deeds” and “Index of Registry Agency fees” are based on the combined data from the PR and Cadaster and are estimated for each individual transaction. “Index of municipality (local) taxes” are based on the municipality tax rates defined each year by the local authorities. “Index of real estate fees” - since 2022 a quarterly survey on the real estate fees is conducted. It addresses a sample of real estate agencies (NACE 68.31) with a significant share on residential market. • O.1.2.1. Major repairs and maintenance: Data source is the survey 'Major repair and maintenance'. Representative sample is drawn from construction and some industrial enterprises, which carry out specific services on major repairs and improvements of dwellings and residential buildings. • O.1.2.2. Insurance connected with dwelling This sub-index is calculated until end of 2021. The source for this sub-index was the information received from insurance companies, which offer property insurance to the individuals. The sampling frame for 2021 included 10 companies which represented 84.5% of the insurance companies operating on the market. • O.1.2.3. Other services related to ownership of dwellings: The annual property taxes are based on the ordinance for local taxes and fees to the main city in the 28 districts in the country. OOH Weights The use of National Accounts data complemented with combined information from the Property Register and the Cadastral Administrative-Information System (CAIS) are considered as the most adequate approach for derivation of OOH weights.
Frequency of data collection	Quarterly, exept for the sub-index „Other services related to ownership of dwellings” for which data is collected annually.
Data collection	Data are collected from administrative datasources, by questionnaires or via Internet.
Data validation	Survey data First validation is done when data are received. There is no automatic rejection of records, each problematic record is considered individually and any necessary modifications are made only on the basis of relevant information. Automatic quality controls have also been implemented in the information system for Major repairs and maintenance. Missing prices are imputed. Administrative data 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.
Data compilation	The overall OOHPI and the sub-indices are calculated using a chained-linked Laspeyres formula. • O.1.1.1.1. Purchases of new dwellings: The “Purchases of new dwellings” indeices are calculated using stratisfication combined with hedonic method. Stratification is based on geographical area (defined at district level) and dwelling type categories. Dwellings are categorized by type of a dwelling (flats, houses). The quarterly compilation of this sub-index 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 price change for each strata; • Aggregation to the upper levels using Lasspeyres formula and calculation of the overall index for new dwellings. 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). A model is estimated for 28 districts of the country and for 6 big cities with population above 120000 inhabitants in order to guarantee a minimum amount of observations in each stratum. The general aggregate index is calculated as a weighted arithmetic average of elementary indices where the weights in year (t) reflect the average annual value of dwellings transaction calculated from the preceding year (t-1) and price updated to 4th quarter of year (t-1). • O.1.1.3. Other services related to the acquisition of dwellings: Stratification method is applied for compilation of sub-indices for ‘Notary deeds’ and ‘Municipality (local) fees’. For compilation of ‘Notary deeds’ index five categories are defined according the amount of the material interest and for each category a 'pure' fixed and proportional taxes are determined. For each transaction, the notary fee is additionally calculated. Next, the average notary fee for each of the observed categories are obtained and base indices are calculated at elementary level. The overall index is Laspeyres type index of the weighted categories’ sub-indices. For compilation of ‘Municipality (local) fees’ index, data are divided into 28 stratums based on geographical location (by districts). Base indices are compiled for each of the 28 districts by adjusting the rate of the municipality tax with the regional House price indices (HPI) to reflect the price evolution of the total expenditure of the dwellings. Next, elementary level sub-indices are aggregated to the total index for the whole country using Laspeyres type formula. The index for ‘Real estate fees’ is based on an average rate of the real estates’ commissions based on results from the survey on real estate fees for the 28 districts in the country. The overall average rate for the country is adjusted with the total HPI (for new and existing dwellings) according the OOH manual. ‘Registry Agency fees’ represent the fees that a purchaser has to pay in Registry agency when the transaction is registered. The tax is available in the PR for each individual transaction. Average tax rate is calculated from the transactions for each of the 28 districts in the country and the estimated rates are adjusted with the regional HPIs according the OOH manual. • O.1.2.1. Major repairs and maintenance: The technique for calculating the overall price index for major repairs and improvements for dwellings consists of several stages/steps: • Calculation of the total prices by types of works, as the sum of the price of materials and labour costs; • Calculation of the elementary price indices of materials, costs of works and total index at the base of the third quarter of 2012; • Calculation of geometric mean sub-indices; • Total index calculated as a sum of weighted sub-indices. • O.1.2.2. Insurance connected with dwelling Untill end of 2021 the stratification approach was applied and the insurance policies of the insurance companies were divided into 4 strata according to the earthquake zones. For each insurance company the average price of four zones was calculated and the overall price index per company. Quarterly total index for insurance companies was aggregated, weighted with net paid premiums, published by Financial Supervision Commission in year (t-2). • O.1.2.3. Other services related to ownership of dwellings: Index for the residential property taxes comprises data for different type of properties and for all 28 district centers of the country. Property tax is derived by a flat rate (in thousands) applied to the tax valuation of a property, for each individual dwelling and is defined each year by local tax authority according the Local Taxes and Fees Act. OOH Weights OOH weights are updated each year and the weights for index calculation in year (t) reflect the average annual value of households' expenditures calculated from the preceding year (t-1) and price updated to 4th quarter of year (t-1). Each year OOHPI are calculated using fourth quarter of the previous year=100 as base period and are rebased to 2015=100 using the chain linked method.
Adjustment	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.
Comment

Download in SDMX 2.1 file format: Owner occupied housing price index (OOHPI)

Metadata Structure Definition in SDMX 2.1: ESMS_MSD+BNSI+2.0+SDMX.2.1.xml

Download in SDMX 2.0 file format: Owner occupied housing price index (OOHPI)

Metadata Structure Definition in SDMX 2.0: ESMS_MSD+BNSI+2.0+SDMX.2.0.xml

Quality reports

ESS Standard for Quality Reports Structure (ESQRS)

Owner occupied housing price index (OOHPI)
Contact
Contact organisation	National Statistical Institute
Contact organisation unit	Consumer Prices, Housing prices and PPP Department
Contact name	Albena Dancheva
Contact person function	Head of Department
Contact mail address	2 Panayot Volov Str., 1038 Sofia
Contact email address	adancheva@nsi.bg
Contact phone number	+359 2 9857 767
Contact fax number
Statistical presentation
Data description	The Owner occupied housing price index (OOHPI) is a quarterly indicator that measures the evolution of the transaction prices of dwellings purchased by owner-occupiers, the changes in the expenditures connected with the acquisition of dwellings, and the cost of other goods and services that households acquire in their role as owners of dwellings. All prices are measured using the net acquisition approach. Under this approach, prices are measured to reflect the change in the cost of goods and services which are new to the hosuehold sector as a whole. Sales between the households are out of the scope of the OOHPI. Indices are based on harmonised definitions and concepts according the Regulation (EU) 2016/792 of the European Parliament and of the Council, Commissin Implementing Regulation (EU) 2023/1470 and described in the OOH Technical Manual.
Classification system	According the Commission Implementing Regulation (EU) 2023/1470 laying down the methodological and technical specifications as regards harmonised indices of consumer prices and the house price index, the classification system for OOHPI includes the following categories: O.1. Owner-occupiers’ housing expenditures O.1.1. Acquisitions of dwellings O.1.1.1. New dwellings O.1.1.1.1. Purchases of new dwellings O.1.1.1.2. Self-build dwellings and major renovations (not observed yet) O.1.1.2. Existing dwellings new to households (not observed yet) O.1.1.3. Other services related to the acquisition of dwellings O.1.2. Ownership of dwellings O.1.2.1. Major repairs and maintenance O.1.2.2. Insurance connected with dwellings (observed until q4’2021) O.1.2.3. Other services related to ownership of dwellings (observed since q1’2015).
Sector coverage	Hoseholds on the territory of the country, which are owner-occupiers, irrespective of the type of area in which they live, their position in the income distribution and their nationality status.
Statistical concepts and definitions	OOHPI compilation follows methodological standards set out in the Technical Manual on Owner-Occupied Housing (OOH) provided by Eurostat to ensure comparability of indices across Member States. Currently ‘Self-build dwelling and major renovations’ and ‘Existing dwellings new to the household sector’ are not calculated. Until achieving the full coverage of OOHPI the data are subject to revisions according to the Commission Implementing Regulation (EU) 2023/1470 of 17 July 2023. The published OOHPI includes the following sub-indices:: • O.1.1.1.1. Purchases of new dwellings: Index figures for the ‘Purchase of new dwellings’ are compiled on the basis of full transaction prices of newly build dwellings that households acquire on the residential market. 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. • O.1.1.3. Other services related to the acquisition of dwellings: The index for ‘Other services related to the acquisition of dwellings’ includes the following four sub-indices: - index of notary deeds; - index of real estate fees; - index of Registry Agency fees; and - index of municipality (local) taxes. • O.1.2.1. Major repairs and maintenance: The price index for ‘Major repairs and maintenance’ is compiled based on a number of pre-defined set of typical activities on major repair and maintenance obtained from enterprises, which execute constraction works on residential buildings. • O.1.2.2. Insurance connected with the dwellings: The index for ‘Insurance connected with the dwellings’ has been discontinued at the end of 2021 due to the low share in households’ expenditures. This sub-index considered the service charges paid by owner occupiers for the kinds of insurance for the structure of his dwelling (e.g.: walls, fences, gates, etc). • O.1.2.3. Other services related to ownership of dwellings: Currently, ‘Other services related to ownership of dwellings’ includes the annual property tax payed to municipalities by each owner of a residential property. The OOHPI sub-indices are chain-linked Laspeyres type’s idices.
Statistical unit	Prices incurred by private households, which are owner-occupiers.
Statistical population	The statistical population consists of all households' expenditures spent for the acquisition of residential property new for the households’ sector and expenditures incurred by households in their role as an owner-occupier.
Reference area	OOHPI cover the whole territory of the country.
Time coverage	Data are available since 2015. Until the end of 2021 ‘Purchases of new dwellings’ index was calculated using sampled survey data. Since 2022 administrative data sources (the Property register complemented with Cadastral data) are introduced, therefore breaks in time series must be considered in Q1 2022.
Base period	2015=100
Statistical processing
Source data	Direct data sources in combination with administrative data are used for compiling OOHPI. OOH Prices • O.1.1.1.1. Purchases of new dwellings: Since 2022 the Property register (PR), maintained by the Registry Agency, in combination with data from the Cadastral Information System (by the Geodesy, cartography and cadaster Agency) are used as data sources for compilation of this sub-index. Until the end of 2021 the data source for compilation of this sub-index is a quarterly survey - 'Survey on the house price indices' that gives information on the market prices of the transacted 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. • O.1.1.3. Other services related to the acquisition of dwellings: “Index of notary deeds” and “Index of Registry Agency fees” are based on the combined data from the PR and Cadaster and are estimated for each individual transaction. “Index of municipality (local) taxes” are based on the municipality tax rates defined each year by the local authorities. “Index of real estate fees” - since 2022 a quarterly survey on the real estate fees is conducted. It addresses a sample of real estate agencies (NACE 68.31) with a significant share on residential market. • O.1.2.1. Major repairs and maintenance: Data source is the survey 'Major repair and maintenance'. Representative sample is drawn from construction and some industrial enterprises, which carry out specific services on major repairs and improvements of dwellings and residential buildings. • O.1.2.2. Insurance connected with dwelling This sub-index is calculated until end of 2021. The source for this sub-index was the information received from insurance companies, which offer property insurance to the individuals. The sampling frame for 2021 included 10 companies which represented 84.5% of the insurance companies operating on the market. • O.1.2.3. Other services related to ownership of dwellings: The annual property taxes are based on the ordinance for local taxes and fees to the main city in the 28 districts in the country. OOH Weights The use of National Accounts data complemented with combined information from the Property Register and the Cadastral Administrative-Information System (CAIS) are considered as the most adequate approach for derivation of OOH weights.
Frequency of data collection	Quarterly, exept for the sub-index „Other services related to ownership of dwellings” for which data is collected annually.
Data collection	Data are collected from administrative datasources, by questionnaires or via Internet.
Data validation	Survey data First validation is done when data are received. There is no automatic rejection of records, each problematic record is considered individually and any necessary modifications are made only on the basis of relevant information. Automatic quality controls have also been implemented in the information system for Major repairs and maintenance. Missing prices are imputed. Administrative data 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.
Data compilation	The overall OOHPI and the sub-indices are calculated using a chained-linked Laspeyres formula. • O.1.1.1.1. Purchases of new dwellings: The “Purchases of new dwellings” indeices are calculated using stratisfication combined with hedonic method. Stratification is based on geographical area (defined at district level) and dwelling type categories. Dwellings are categorized by type of a dwelling (flats, houses). The quarterly compilation of this sub-index 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 price change for each strata; • Aggregation to the upper levels using Lasspeyres formula and calculation of the overall index for new dwellings. 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). A model is estimated for 28 districts of the country and for 6 big cities with population above 120000 inhabitants in order to guarantee a minimum amount of observations in each stratum. The general aggregate index is calculated as a weighted arithmetic average of elementary indices where the weights in year (t) reflect the average annual value of dwellings transaction calculated from the preceding year (t-1) and price updated to 4th quarter of year (t-1). • O.1.1.3. Other services related to the acquisition of dwellings: Stratification method is applied for compilation of sub-indices for ‘Notary deeds’ and ‘Municipality (local) fees’. For compilation of ‘Notary deeds’ index five categories are defined according the amount of the material interest and for each category a 'pure' fixed and proportional taxes are determined. For each transaction, the notary fee is additionally calculated. Next, the average notary fee for each of the observed categories are obtained and base indices are calculated at elementary level. The overall index is Laspeyres type index of the weighted categories’ sub-indices. For compilation of ‘Municipality (local) fees’ index, data are divided into 28 stratums based on geographical location (by districts). Base indices are compiled for each of the 28 districts by adjusting the rate of the municipality tax with the regional House price indices (HPI) to reflect the price evolution of the total expenditure of the dwellings. Next, elementary level sub-indices are aggregated to the total index for the whole country using Laspeyres type formula. The index for ‘Real estate fees’ is based on an average rate of the real estates’ commissions based on results from the survey on real estate fees for the 28 districts in the country. The overall average rate for the country is adjusted with the total HPI (for new and existing dwellings) according the OOH manual. ‘Registry Agency fees’ represent the fees that a purchaser has to pay in Registry agency when the transaction is registered. The tax is available in the PR for each individual transaction. Average tax rate is calculated from the transactions for each of the 28 districts in the country and the estimated rates are adjusted with the regional HPIs according the OOH manual. • O.1.2.1. Major repairs and maintenance: The technique for calculating the overall price index for major repairs and improvements for dwellings consists of several stages/steps: • Calculation of the total prices by types of works, as the sum of the price of materials and labour costs; • Calculation of the elementary price indices of materials, costs of works and total index at the base of the third quarter of 2012; • Calculation of geometric mean sub-indices; • Total index calculated as a sum of weighted sub-indices. • O.1.2.2. Insurance connected with dwelling Untill end of 2021 the stratification approach was applied and the insurance policies of the insurance companies were divided into 4 strata according to the earthquake zones. For each insurance company the average price of four zones was calculated and the overall price index per company. Quarterly total index for insurance companies was aggregated, weighted with net paid premiums, published by Financial Supervision Commission in year (t-2). • O.1.2.3. Other services related to ownership of dwellings: Index for the residential property taxes comprises data for different type of properties and for all 28 district centers of the country. Property tax is derived by a flat rate (in thousands) applied to the tax valuation of a property, for each individual dwelling and is defined each year by local tax authority according the Local Taxes and Fees Act. OOH Weights OOH weights are updated each year and the weights for index calculation in year (t) reflect the average annual value of households' expenditures calculated from the preceding year (t-1) and price updated to 4th quarter of year (t-1). Each year OOHPI are calculated using fourth quarter of the previous year=100 as base period and are rebased to 2015=100 using the chain linked method.
Adjustment	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.
Quality management
Quality assurance	All data are checked for completeness and consistency with statistical concepts and definitions. OOHPI are produced in compliance with the methodological requirements of the Owner-Occupied Technical Manual. Automatic quality controls have been implemented within the production process in order to detect and correct errors. Outliers are excluded from calculations.
Quality assessment	The quality of the OOHPI is routinely reviewed using a framework that is based on the OOH technical manual and the European Statistical System (ESS) definition of quality.
Relevance
User needs	No information.
User satisfaction	None.
Completeness	OOH sub-indices 'O.1.1.2 Existing dwellings new to households' and 'O.1.1.1.2. Self-build dwellings and major renovations' are still excluded from OOHPI calculation. Since 2022 the sub-index for 'O.1.2.2 Insurance connected with dwellings' is not compiled due to the low share (under the treashold) in households' expenditures.
Data completeness - rate
Accuracy and reliability
Overall accuracy	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. There is a variety of data sources both for weights (administrative data, statistical data from National Accounts, Construction Statistics, annual reporting of the enterprises, Statistics on Population and Housing fund Department, etc.) and prices (survey data, administrative data, construction companies, real estate agents, insurance companies, municipalities, etc.) for compilation of OOHPI sub-indices. In cases where surveys are used the type of survey and the price collection methods are designed to ensure sufficient coverage and timeliness.
Sampling error	Sampling errors are not calculated for OOHP indices.
Sampling errors - indicators
Non-sampling error	Non-sampling errors are not quantified for the OOHPI. NSI tries to reduce non-sampling errors through continuous methodological improvements of data collection, validation and data management, which help us to avoid coding and typing errors.
Coverage error
Over-coverage - rate
Common units - proportion
Measurement error
Non response error
Unit non-response - rate
Item non-response - rate
Processing error
Imputation - rate
Model assumption error
Seasonal adjustment
Data revision - policy	OOHPI are revisable under the terms of Regulation (EU) 2016/792 of the European Parliament and of the Council, and Commission Implementing Regulation (EU) 2023/1470 of 17 July 2023. Published OOHPI may be revised for mistakes, new or improved information and methodological improvements.
Data revision - practice	OOHPI are published as preliminary and are usually confirmed or revised in the following quarter.
Data revision - average size
Timeliness and punctuality
Timeliness	Data are published according to NSI Release calendar - 85 days after the end of the observed quarter.
Time lag - first results
Time lag - final results
Punctuality	Data are always delivered and published on the pre-announced release dates.
Punctuality - delivery and publication
Coherence and comparability
Comparability - geographical	OOHP indices are only compiled on country level. Reagional indices are not available. However, OOHPI are developed according a common framework elaborated at European level and therefore, are commpareble across European countries.
Asymmetry for mirror flows statistics - coefficient
Comparability - over time	Since first quarter of 2015 until fourth quarter of 2021 OOHPI are fully comparable over time. Due to transition towards administrative data source for calculation of “Purchase of new dwellings”, a break in time series must be considered in the first quarter of 2022.
Length of comparable time series
Coherence - cross domain	OOHPI sub-indices are checked for coherence with the HPI sub-indices. Calculation of "Purchase of new dwellings" comprises the same number of transactions for both datasets but differ by the used weights. Weights for the compilation of OOHPI sub-index 'Purchase of new dwellings' are net of value of transactions from households to non-household’s sectors.
Coherence - sub annual and annual statistics
Coherence - National Accounts
Coherence - internal	OOHPI are internally coherent. Higher level aggregations are derived from detailed indices in accordance with strictly-defined procedures.
Accessibility and clarity
News release	None.
Publications	None.
On-line database	OOHPI are available to all users on the NSI website under the heading Housing price statistics: http://www.nsi.bg/en/node/13023
Data tables - consultations
Micro-data access	Microdata are not diseminated.
Other	None.
Metadata - consultations
Documentation on methodology	EU and EC regulations: http://ec.europa.eu/eurostat/web/housing-price-statistics/legislation
Metadata completeness – rate
Quality documentation	Quality report in ESS Standard for Quality Reports Structure (ESQRS) - https://www.nsi.bg/en/content/13025/housing-price-statistics
Cost and burden
Confidentiality
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. http://www.nsi.bg/sites/default/files/files/pages/LegalBasis_e/Consolidated_version_of_amended_Regulation_223_2009_EN.pdf
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.
Comment