Statistical Office of the Republic of Slovenia — SURS

Price Statistics Section, webpage

Statistical Office of the Republic of Slovenia

Litostrojska cesta 54
SI-1000 Ljubljana
SLOVENIA

The harmonised index of consumer prices (HICP) is a consumer price index (CPI) that is calculated according to a harmonised approach. It measures the change over time of the prices of consumer goods and services acquired by households (inflation).

Due to the common methodology, the HICPs of the countries and European aggregates can be directly compared.

European classification of individual consumption according to purpose (ECOICOP)

The HICP covers the final monetary consumption expenditure of the household sector.

The main statistical variables are price indices.

The basic unit of statistical observation are prices for consumer products.

3.6.1. Statistical target population

The target statistical universe is the 'household final monetary consumption expenditure' (HFMCE) on the economic territory of the country by both resident and non-resident households. The household sector to which the definition refers, includes all individuals or groups of individuals irrespective of, in particular, the type of area in which they live, their position in the income distribution and their nationality or residence status. These definitions follow the national accounts concepts in the European System of Accounts.

3.6.2. Coverage error population

There are no deviations from the target population.

3.7.1. Geographical coverage

The HICP refers to the economic territory of a country as referred to in paragraph 2.05 of Annex A to ESA 2010, with the exception that the extraterritorial enclaves situated within the boundaries of a Member State or a country are included and the territorial enclaves situated in the rest of the world are excluded.

3.7.2. Coverage error regions

The economic territory of Slovenia is the same as the geographic territory on which Slovenian government institutions conduct administrative control. The HICP covers the entire area of the country.

3.8.1. Start of time series

The HICP series started in January 1997.

3.8.2. Start of time series - national specifics

The production of HICP started in 2001. From 1997 to 2000, the data for CPI and HICP are considered as equal.

See the HICP database

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).

HICP is a monthly statistics.

Harmonised Indices of Consumer Prices (HICPs) are harmonised inflation figures required under the Treaty on the Functioning of the European Union. Regulation (EU) 2016/792 of the European Parliament and the Council of 11 May 2016 (OJ L 135) sets the legal basis for establishing a harmonised methodology for the compilation of the HICP and the HICP-CT.

This regulation is implemented by Commission Regulation (EU) 2020/1148 of 31 July 2020.

Further documentation, can be found in Eurostat’s website - HICP dedicated section, namely recommendations on specific topics, under the methodology page, and guidelines, under the quality page.

Data are sent to Eurostat via eDAMIS following a predetermined timetable.

The legal basis for confidentiality treatment is based on 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 and the National Statistics Act (OJ RS, No. 45/95 and 9/2001).

The National Statistics Act (hereinafter the ZDSta) stipulates within fundamental principles of national statistics in Article 2 that 'national statistics shall be implemented on the principles of … confidentiality …' The principle is concretised in further provisions of the ZDSta, while for an explanation one can turn to some international documents.

The United Nations Resolution on Fundamental Principles of Official Statistics (adopted by the UN Statistical Commission in 1994 and confirmed by the UN General Assembly on 29 January 2014) determines in Principle 6 that 'individual data collected by statistical agencies for statistical compilation, whether they refer to natural or legal persons, are to be strictly confidential and used exclusively for statistical purposes'. The explanation of the resolution is that reliable official statistics rely on the public's trust and goodwill to provide timely and accurate data that are requested. Such cooperation is only possible if statistical confidentiality is respected.

In a similar way, this principle is concretised in the European Statistics Code of Practice (adopted by the European Statistical System Committee on 16 November 2017), which determines that 'the privacy of data providers (households, enterprises, administrations and other respondents), the confidentiality of the information they provide and its use only for statistical purposes must be absolutely guaranteed'.

And last but not least, item (e) of Article 2 of Regulation (EC) No. 223/2009 on European Statistics determines statistical confidentiality as 'the protection of confidential data related to single statistical units which are obtained directly for statistical purposes or indirectly from administrative or other sources and implying the prohibition of use for non-statistical purposes of the data obtained and of their unlawful disclosure'. 

Statistical confidentiality as determined above is thus provided with the help of various legal, organisational and technological procedures that can be summarised in the following points:

• Security of data and information
• Use of data exclusively for statistical purposes
• Statistical protection of the data transmitted to users
• Secure management of data for research purposes
• Educating and informing the employees about statistical confidentiality

Only indices (at the Ecoicop level) and the average annual retail prices for some products and services where there is no confidentiality issue are published. Confidential data are data at the level of each unit, the data on item weights and the most detailed descriptions of products and services.

In line with the Community legal framework and the European Statistics Code of Practice Eurostat disseminates European statistics on Eurostat's website (see point 10 - 'Accessibility and clarity') respecting professional independence and in an objective, professional and transparent manner in which all users are treated equitably. The detailed arrangements are governed by the Protocol on impartial access to Eurostat data for users.

The HICP is released according to Eurostat’s Release calendar.

The calendar is publically available and published at the end of the year for the full following year.

First data are published in accordance with the release calendar as First Release at 10:30 (local time) on the day of release.

SURS's advance release calendar is available on the website and can also be subscribed via email or RSS.

The release policy is oriented towards the wide public. The release dates are published in advance and are listed in a release calendar. In addition to the release calendar, SURS also prepares press conferences (invitations are sent to journalists) on special events or releases of important analyses of statistical data. On the other hand, all subscribers to the news are informed about the release a week prior to the data release.

Preliminary access to the data of the first release was provided to the Prime Minister's Office (2-18 hours before the publication) from January 2022 to May 2022. In the following months of the year, preliminary access was no longer available.

Statistical data can be obtained on Statistical Office's web pages: Prices and Inflation, and also via mail, phone, fax and e-mail, by ordering statistical publications and by visiting the Information Centre during office hours.

Monthly

Harmonised consumer price indices are produced monthly. Dissemination policy and practice:

• Electronic dissemination
  • monthly: through E-mail, Twitter, RSS and via Edamis, users can also subscribe to automatically receive alerts when the First Release is released,
  • annually: Stat’o’book (Statistical overview of Slovenia).
• Paper dissemination
  • Stat’o’book and occasional publications such as Prices in Slovenia (published in 2012).

Dissemination languages are Slovenian and English.

Publication dates for CPI/HICP are set forth in advance. HICP data are just a small part of a news release, where the all-items HICP and detailed HICPs (for 12 main ECOICOP Divisions, plus special aggregates goods and services) are available to the public. The focus of the news release is on CPI.

Data on HICP are a part of the First release of Consumer price indices and of some other publications.

HICP database are available on Database - Harmonised Indices of Consumer Prices (HICP) - Eurostat (europa.eu)

Micro-data are not disseminated.

SURS grants special access (i.e. access to microdata) mostly to researchers and institutions, but strictly on the basis of a special protocol: http://www.stat.si/StatWeb/en/StaticPages/Index/For-Researchers.

Non-applicable.

The HICP Methodological Manual provides the reference methodology for the production of HICP. (https://ec.europa.eu/eurostat/web/products-manuals-and-guidelines/-/KS-GQ-17-015)

10.6.1. Documentation on methodology - national specifics

A description of the methodology and sources used to compile the HICP are published on Statistical Office's website: www.stat.si/StatWeb/ under the Methodology tab.

This document is updated and published in February each year and refers to the current year.

Annual quality reports for the survey CPI and HICP are available on the web page Consumer price index (CPI), Harmonised Index of Consumer Prices (HICP) (stat.si)

European statistics code of practice.

11.1.1. Quality management - Compliance Monitoring

Compliance Monitoring

11.1.2. Quality assurance - national specifics

Guidelines for quality assurance were updated in 2017. They are divided into eight fields: analysis of needs and requests, survey design and preparation, selection of observation units, data collection, data processing, data analysis, data dissemination, and documentation and evaluation of surveys. These Guidelines stand for all SURS’s Divisions, including HICP.

Quality reports for the CPI and HICP survey are published on our website. 

In a case of deviations data are checked manually. We have contacts with price collectors on regular basis.  In addition, each collector’s work is supposed to be checked in the field 1-2 times per year to ensure that central office guidance is being followed. Many stages of the production process are automated in order to reduce human error. In case the price controller decides that the price collector’s explanation is not enough, it is demanded of the price collector to check e.g. the price again and report it to the section.

11.2.1. Compliance monitoring - last report and main results

The last available compliance or follow-up report can be found in Eurostat’s web page Quality - Harmonised Indices of Consumer Prices (HICP) - Eurostat (europa.eu)

 Direct links:

• HICP Compliance Monitoring Report, Slovenia, 2016
• Follow-up report HICP Compliance Monitoring report, Slovenia, 2019

11.2.2. Quality assessment - national specifics

HICP indices are produced in compliance with HICP methodological requirements and standards. The HICP process is still being developed (new data sources and related adaptation of methodology).

In addition to being a general measure of inflation, the HICP is also used in the areas of:

• wages, social benefit and contract indexation;
• economic forecasting and analysis;
• measuring specific price trends;
• accounting purposes and deflating other series;
• inflation targeting by central banks;
• cross-country economic comparisons.

The euro area (evolving composition) index is used by the European Central Bank (ECB) as the main indicator for monetary policy management. The ECB and the European Commission's Directorate-General for Economic and Financial Affairs (DG ECFIN) use the HICP for assessing price stability and price convergence required for entry into European Monetary Union.

Other users include: National Central Banks, financial institutions, economic analysts, the media and the public at large.

12.1.1. User Needs - national specifics

HICP is a general measure of inflation in cross-country economic comparisons, used mostly by financial institutions for monetary policy (ECB, National Bank, etc.), European and international organisations (Eurostat, IMF, OECD, ILO), the national government, ministries, agencies, many sections within SURS, media, news agencies, enterprises and public as well.

SURS constantly monitors the satisfaction and needs of users of our statistical data and improves products and services based on their opinions and suggestions.

In 2021, the level of general satisfaction with SURS was assessed on the basis of three statements: overall satisfaction with SURS (average score 8.3), fulfilment of expectations (average score 8.2) and recommendation of SURS as a source of statistical data (average score 8.8). In 2021, all average scores were higher than in 2020. 

Users' opinions and needs are also monitored by the exchange of views within the Price Statistics Advisory Committee. The principal users are asked about their needs, wishes and interests at the regular meetings.

The Board of users is represented in the advisory committee. The Statistical Advisory Committee (for prices) is composed of outside members and SURS members. The outside members are representatives of relevant ministries, Bank of Slovenia, IER (Institute for Economic Research), FURS (Financial Administration of the Republic of Slovenia), ZPS (Slovene Consumers' Association), GURS (Surveying and Mapping Authority of the Republic of Slovenia), the Slovenian Chamber of Commerce, the EIPF Economic Institute, UMAR Institute of Macroeconomic Analysis and Development, the Faculty of Economics Ljubljana and Maribor, ZSSS (the Association of Free Trade Unions of Slovenia), ZDS (Association of Employers of Slovenia) and others.

Meetings are held every year and a half. All users of our data are invited. Its instructions are not strictly binding, but statistical advisory committees have a significant impact on the development of national statistics in Slovenia at the expert level and in cooperation with institutions in common efforts to provide quality, timely and relevant statistics.  We often ask their opinion on the cancellation of individual surveys and major revisions. We inform them about all major methodological changes we are planning to perform.

In addition, there is the Methodological Council, which is meant for professional discussion of outstanding issues, methodological changes, carrying out surveys, strategy, etc., and it consists of experts from various fields. For major changes proper material must be prepared and Council’s guidelines, recommendations and conclusions are binding.

All statistics that are required by international standards are calculated. HICP covers all the groups and subgroups of the ECOICOP classification whose share in total consumption is greater than 0.1%. Indices at the 5-digit level are produced.

As required, HICP-CT covers each tax category which on its own covers 2% or more of the total tax revenue from all taxes. Taxes accounting for a minimum of 90% of total revenue of taxes are kept constant. Indices at the 5-digit level are produced.

The accuracy of source data is monitored by assessing the methodological soundness of price and weight sources and the adherence to the methodological recommendations. The goods and services selected for the basket are those that are most important to the customers; have a significant share in total consumption; their price movement also best reflects the price movement for similar goods or services. All methodology recommendations are taken into account. Prices are collected in outlets, craftsmen, supermarkets, etc., in four big cities in the country and some other cities, some of them also via the internet and by phone. They reflect the price situation for the whole country. Scanner Data (for the first two ECOICOP Divisions) are obtained from the biggest supermarket chains (covering the whole country).

Weights are based on the data from NA on the structure of household final consumption expenditure.

The outlets from which prices are collected are chosen to represent the existing trade and service network and are based usually on the following criteria: turnover, representativeness and coverage of availability of goods and services included in HICP's basket. Scanner Data are gained from the biggest supermarket chains in the country.  

Private households are included irrespective of their income. The domestic concept is in force.

The survey is not based on a random sample, so we cannot use the 'classic' approaches to assess the sampling error. The methodology for calculating the precision of consumer price indices is not yet completely developed because of the complexity of the sample design.

Non-sampling errors are not quantified.

SURS tries to reduce non-sampling errors through continuous methodological improvements and survey process improvements.

• Survey data: a new data collection application running on PC tablets for survey data was introduced (2016), meaning less possibility of input errors.
• Scanner data: SURS’s application META SOP (SAS) for logic controls and data management is in force as well as visual inspection of indices (2018).
• Web scraping: SURS’s application META SOP (SAS) for logic controls and data management is in force as well as visual inspection of indices (2023).

The full set of HICPs is published each month according to Eurostat’s Release calendar, usually between 15 and 18 days after the end of the reference month.

Each year, the January release is published at the end of February to allow for the annual update of the weights, both of individual product groups and the relative country weights of Members States in the country group aggregates.

The euro area flash estimate is published on the last working day of the reference month or shortly after that.

Since the March 1997, launch of the HICP release, the HICP for the country groups aggregates has always been published on the dates announced in Eurostat’s Release calendar.

HICPs across the Member States aim to be comparable. Any differences at all levels of detail should only reflect differences in price changes or expenditure patterns.

To this end, concepts and methods have been harmonised by means of legislation. HICPs that deviate from these concepts and methods are deemed comparable if they result in an index that is estimated to differ systematically by less than or equal to 0.1 percentage points on average over one year against the previous year (Article 4 of Council and Parliament Regulation (EU) 2016/792).

HICP data are fully comparable over time. There have been several improvements in methodology since the HICP was introduced with the aim of improving the reliability and comparability of the HICP.

There were no breaks in the HICP series despite some significant changes, such as New seasonal regulation (in 2011), Ecoicop classification (in 2017), Scanner Data (in 2018) and bulk web scrapping (in 2023).

There are no considerable differences between CPI and HICP, except that HICP is based on the domestic concept of consumption, while national CPI is based on the national concept of consumption. This difference between the two is in weights.

Annual CPI and HICP indices by months, 2022 

S2 = I_HICP – I_CPI = 109.3-108.8 = 0.5

The HICPs are internally coherent. Higher level aggregations are derived from detailed indices according to well-defined procedures.

Not available

The HICP series, including back data, is revisable under the terms set in Articles 17-20 of Commission Implementing Regulation (EU) 2020/1148.

17.1.1. Data revision - policy - national specifics

Methodological explanation on the revision of statistical data is available on http://www.stat.si/dokument/5299/RevisionOfStatisticalDataMEgeneral.pdf

Major changes in methodology are announced in advance, while information on minor methodological changes is provided in methodological explanations and on Statistical Office's website htttp://www.stat.si/StatWeb/en/home.

In general, monthly indices are not subject to revision. The data are final when first released and if subsequently an error is found, a correction of the First Release is made and users are informed. At the same time, if necessary, the corrected data are transmitted to Eurostat. 

There were two unplanned revisions (June 2013 and December 2019). The main reason was subsequently discovered errors (an error at input data-human error) which had an impact on lower Ecoicop levels and on Total Index as well. When discovered, the entered data were corrected, indices recalculated and the First Release revised. There was no impact on previously published figures.

18.1.1. Weights

Weights used for index calculation in an individual year are based on national accounts data on household final consumption expenditure. These data are checked and updated with data from other statistical and non-statistical sources. The main source for calculating weights is national accounts data (t-2) which are the basis for determining weights at 2^nd, 3^rd, 4^th and in some cases at 5-digit sub-class ECOICOP level, while for lower levels mostly data from the household budget surveys (HBS) are used. Weights are changed every year. All weights are reviewed (sublevels included) every year and updated when required. The weights for 2023 were calculated according to the Guidance on the compilation of HICP weights in case of large changes in consumer expenditures (Eurostat) in order to be representative and to capture a shift in households expenditure patterns in the year t-1 (year t-2 was still significantly impacted by the Covid-19 pandemic).

18.1.1.1. Compilation at elementary aggregate level

Below the level of ECOICOP class we use detailed weights to aggregate item indices to ECOICOP classes. Within item indices we use either regional stratum weights for locally collected items or regional and/or provider/supplier stratum weights for centrally collected items. This applies to ECOICOP 03-12. For food, beverages and tobacco (ECOICOP 01 and 02) at elementary aggregate levels weights are based on the ratio of retailers’ turnover (t-1). The lowest level with explicit weights is the unofficial COICOP 6-digit level (elementary aggregate), e.g. Telecom operators, Financial services and Retailers’ Scanner data on turnover.

For some groups, weights are additionally checked with data from other sources (energy, trade) and, if necessary, corrected (alcoholic beverages, tobacco, cars, fuels, energy). The main reason is that data gained from the HBS is not entirely dependable and complete. Since those groups are very important, data are checked and, if necessary, corrected.

The main source for weights is National accounts data. Weights are additionally updated with data from other sources, i.e. surveys conducted by SURS (retail trade statistics, energy statistics, transport statistics, etc.). These additional sources enable the distribution of weights to aggregate levels with better precision and therefore better quality of weights for the goods and services.

All weights are reviewed every year and updated when required.

For locally collected items, the regional stratum weights for localities are largely derived from the number of people living in each region. For centrally collected items, when one price is valid for the whole county (e.g. newspapers, fuels, etc.), no weights are required. For other centrally collected items, regional weights are derived from population and turnover data along with information from other sources (e.g. providers of goods/services and research agencies, etc.).

Outlets are implicitly weighted via the sampling frame used, i.e. the bigger the market share (turnover) of a retail chain of outlets, the more branches of that chain are sampled. Information for this comes from a retail sales survey. Where no turnover data exist for a particular product or type of outlet, outlets are equally weighted.

For item weights, the main source of information is detailed HBS data. In those cases where the HBS is not so detailed, this information is also supplemented with information from other sources, e.g. providers of goods/services (travel agencies, providers of mobile phone services, financial services, internet, profit rents, number of beds in hotels, etc.), economic and market analyses and other surveys conducted by SURS.

For ECOICOP 01 and 02 (Scanner Data) elementary aggregate levels weights are based on the ratio of retailers’ turnover (t-1).

18.1.1.2. Compilation of sub-index weights

In 2023, the compilation of sub-index weights started with the most recent version of t-1 expenditures, as available from the national accounts, including the ECOICOP breakdown (to sub-class level). The national accounts made the best possible estimates for the 2022 FHCE and Household Final Monetary Consumption Expenditure including the ECOICOP breakdown by classes at 4-digit ECOICOP.

Weights for the HICP for 2023 are thus based on the final data for 2021 and estimated data from national accounts for 2022, taking into account the average change between the 2022 average and December 2022, which is also the price reference period.

Some adjustments were made according to recommendations, by using data from short term statistics. Most of it was already taken into account in the national accounts section when they prepared an estimation of 2022 expenditure shares. 

The biggest changes in weights compared to the previous year are in these ECOICOPs: an increase in 04.5.5., 07.2.2. and a decrease in group Communications and Furnishing, household equipment and routine household maintenance.

For some groups, weights are additionally checked with data from other sources (energy, trade) and, if necessary, corrected. The main reason is that data gained from the HBS is not entirely dependable and complete. Since those groups are very important, data are checked and, if necessary, corrected. We consider data from other sources, i.e. surveys conducted by SURS (retail trade statistics, energy statistics, transport statistics, etc.). These additional sources enable the distribution of weights to aggregate levels with better precision and therefore better quality of weights for the goods and services. 

18.1.1.3. Compilation of sub-index weights

Weights for 2023 are compiled in accordance with Eurostat recommendations. 

They are based on the final data for 2021 and estimated data from national accounts for 2022, taking into account the average change between the 2022 average and December 2022, which is also the price reference period.

18.1.1.4. Weights – plausibility checking

Normally (with the exception of 2021-2023), weights are obtained from National Accounts for higher ECOICOP levels and are complemented with HBS data on the lower level (elementary aggregate level). These data are checked and updated with data from other statistical and non-statistical sources. Nevertheless, the main source for calculating weights is national accounts data (t-2). Weights are changed every year. Weights are price-updated to December prices (t-1). Weights for important and sensitive groups (critical weights like Motor cars, Fuels and lubricants for personal transport equipment) are additionally reviewed and updated every year with data t-1.

Since 2018, a new data source (retailers’ turnover from Scanner Data) is taken into account (this applies to lower levels of aggregation). All weights are reviewed (sublevels included) every year and updated when required.

In accordance with the ECOICOP classification some groups, classes and sub-classes are not part of the Slovenian CPI/HICP calculation; that goes for goods and services which are either not relevant or their expenditure is zero or below the threshold (their expenditures are redistributed to the higher level within the same group).

18.1.1.5. Price updating

Price updating to December t-1 is made with the difference between the average of 2022 and December 2022, according to recommendations.

Price updating is applied at the sub-class level, that is ECOICOP5 level.

18.1.1.6. Compilation of total household final monetary consumption expenditure

Country weights were estimated by the national accounts section. Many aggregates of HFMCE were estimated directly from the domestic concept of FCHE. Net purchases abroad data were estimated directly from the balance of payments.

For the 4th quarter, we did estimation by two methods. The first was done with using the same indices as they were in the first three quarters and the second estimation was done using monthly data like overnight stays of tourists.

The heading Income (mainly own account production) was assessed according to preliminary data of Economic accounts for agriculture, while other components remain unchanged, due to the fact they are relatively stable through the last years. 

18.1.2. Prices

SURS has a mixed approach regarding price collection:

• prices are collected directly in the field or via telephone, emails, catalogues, the internet,
• in electronic form,
• by web-scraping,
• by scanner data. 

18.1.2.1. Data Source - overview  

The main sources of price data used to compile the HICP are survey data, scanner data and web scraping.

18.1.2.2. Scanner data - general information

Scanner Data are received from Supermarkets and serve as:

• the only source for index computation for Ecoicop Divisions 01 and 02. The share of supermarket data represents about 75% of the grocery market (ECOICOP 01) and 70% (ECOICOP 02 - Alcohol). Market shares (2015) were calculated as the enterprise’s turnover as a share of turnover of all enterprises registered in Retail sales in non-specialized stores with food, beverages or tobacco predominating.
• for Ecoicop 03, 05, 06, 07, 09 and 12 as a source for price observation, but just in a function of imitating field collection (compliments traditional stores).

18.1.2.3. Web scraping - general information

SURS performs bulk web scraping but only a limited number of data enter index production - for now we just mimic traditional price collection.

We scrape data from the biggest domestic stores selling computers, computer equipment and package holiday providers (where access is not rejected).

Targeted web scraping

SURS performs targeted web scraping with a limited number of data enter index production (mimicking traditional price collection) for the following groups: 09.6, 09.1.3.3 and for one elementary aggregate in 09.5.4.9.

Bulk web scraping

In 2023, a new index calculation methodology is in force for 09.1.3.1 Information processing equipment and a part of 09.1.3.2 Accessories for information processing equipment. 

18.1.3. Sampling

18.1.3.1. Sampling design: locations for survey

For the purpose of collecting data on prices, the country is divided into four parts ('regions'). Within 'regions', the largest city with surroundings is chosen for price collection (i.e. Ljubljana, Maribor, Koper and Novo mesto). Some prices are collected in other big cities, too, or centrally by the section, so that practically the entire territory of Slovenia is covered. Besides that, Scanner Data are obtained from the biggest supermarket chains (covering the whole country).

18.1.3.2. Sampling design: outlets

Outlets in each location are firstly selected on the basis of the turnover data from retail trade statistics as well as from information from the business register and other sources. Then the outlet sample is further augmented by price collectors’ experience and knowledge of the local market. We monitor prices in different types of outlets: markets, specialized stores, discounters and craftsmen. From 2018, we exclude market stalls, fish shops, butcheries, and bakeries (they are not important in consumers‘ shopping habits, at least not on a significant scale).

18.1.3.3. Sampling design: newly significant goods and services

The list of newly introduced goods and services in 2023: Electric bicycles.

Price data is collected every month.

18.3.1. Price collection surveys

Price collectors collect prices by tablet computer (software based on Windows universal application). These data are sent by the http protocol to the SQL server at the central office. Data are reviewed once again and sent to Oracle where they are stored and prepared for further processing. The main difference between price collectors in the field and central price collectors is that in the central office prices are monitored on the internet, obtained from scanner data and web scraping; however, prices from the internet and web scraped data must be entered into the tablet, too. There is one price collector per locality where prices are collected. Taking up their duties, new employees visit shops accompanied by someone experienced in this area (for some time). But first of all, a tablet computer and its software used daily at work are presented. They also get all the necessary written instructions for price collection by tablet computer and clarifications concerning the functioning of the device. Additionally, we also organize 2-3 special meetings per year with price collectors, where the current problems in the field, new developments and new regulations from the harmonization process are discussed. Price collectors are experienced and in touch with the market. Their influence in outlet sampling, updating of the basket and marking the items for quality adjustments are significant.

Without taking into account prices for the first two Ecoicop Divisions, more than a third of all prices are collected centrally via telephone, emails, catalogues, electronic form, scanner data, web scraping and the internet; for newspapers and periodicals, post and telecommunication services, package holidays, accommodation services, electricity and fuel prices, prices for some medicaments and vehicles, bank services, municipal services, etc. Furthermore, scanner data are obtained from supermarket chains (covering household maintenance products, personal hygiene products, pets products, etc.), so more and more prices are collected centrally.

18.3.2. Timing of price collection

Data on prices are collected between the 1st and 25th day of each month.

Different data sources have been checked separately. In the case of scanner data, the process fails (reports an error) at the entrance in case data arrive in a different standard, structure or date to which data relate. For traditionally collected prices the number of outlets and items has been checked. That number must be the same as predefined in the base period; the same applies to base prices. All collected prices are reviewed by price collectors before being sent to the central office; but initially, the first phase of control is incorporated in the tablet computer program for data entry and in the end all data are manually checked by a person in the unit. If there are doubts about the reliability of one or several prices, these prices are checked once again by contacting price collectors or, if necessary, checked directly in the field. There is no automatic rejection of observed prices in our validation process. Each case (problematic price) is considered individually and all modifications are done on the basis of relevant information. In addition, each collector's work is checked in the field 1-2 times per year to ensure that central office guidelines are being followed.

Testing the correctness and plausibility of outcomes is performed with several procedures; For Scanner data and bulk web scraping SURS’s application META SOP (SAS) for logic controls and data management is in force as well as visual inspection of indices.

18.4.1. Data validation - price data

Detecting data entry errors: We have several controls. 'Colour warnings' at price entry for monthly indices greater than 110 or smaller than 90. In the case of big discrepancies in price change (index greater than 300 or smaller than 50) additional confirmation of data entry is required. The price collector enters the type of data entry, e.g. number 2 stands for the same product–different price, besides that for data consistency an appropriate remark is chosen (price increase, decrease, discount, etc.), while at larger changes in prices, the price collectors write additional notes when entering the price. In case the price controller decides that the price collector's explanation is not enough, it is demanded of the price collector to check the price again and report it to the section. For simpler data control (conducted by price collectors), the tablet computers’ application enables data to be displayed in Excel (sorting, comparing data, etc., in a way price collectors want). Price collectors can transmit data to the SQL server daily. So none of the collected prices that present a problem are eliminated automatically but are treated individually and additional information on it is collected. In case the specification of the good or service is significantly changed, the section implements quality adjustment.

The monitoring of the consistency of the price information over time is integrated into the tablet's software. At each price entry in the tablet, a numeric remark describing the product’s permanency is required: whether the product is the same as the previous month or it was replaced, etc. So we can monitor the product throughout the year. The consistency of the price information across similar products in the same period is monitored by visual inspection and the information we receive. E.g.: Company X advertises a 20% discount on items with brand Y. Those items are monitored in different outlets/cities, so a 20% discount should be captured everywhere. 

In the case of extreme prices or price changes in Ecoicop 01 and 02 (Scanner data), extreme price changes are considered outliers; for ECOICOP 03-12 price collectors check extreme price changes once again and if there is no acceptable explanation prices are being imputed (previous month’s data).

Scanner data: SURS’s application META SOP (SAS) is designed for logic controls and data management. It removes duplicates and zero values, detects outliers, etc. 

Bulk Web scraping: for bulk web scraping the entire process is automatized. Checkpoints for data validation are integrated at multiple stages. Differences in the quantity of scraped items, major price changes and irregularities in product descriptions are detected.

18.5.1. Elementary price index formulae

The Slovenian HICP is an annually chain-linked Laspeyres-type index.

The price indices for elementary aggregates are calculated as a ratio of geometric mean prices.

The number of decimals applied at:

• Price monitoring - as many decimals are considered as shown on the price lists. At low prices, the calculation per unit takes into account a larger number of decimals. Almost all prices have been applied with 2 decimal places; some exceptions are petrol prices (3 decimals), electricity prices (5 decimals), etc.
• Weights - no rounding or truncation is applied. For weights 7 decimals are applied and transmitted to Eurostat.
• The compilation and transmission of index figures and rates of change - no rounding or truncation for weights is applied. In compilation and transmission to Eurostat 10 decimals are applied. Publication of index figures and rates of change - data are published to 1 decimal, except for the indices 2015 average, where two decimals are displayed.

For the publication of index figures and rates of change, rounding is used.

18.5.2. Aggregation of different data sources

The average national price of each non-food product or service is calculated with weighted arithmetic mean from previously calculated average prices in the locality. From average national prices in each current and base month (December of the previous year) we calculate an individual index for each elementary aggregate.

Data from retailers’ databases (scanner data): From the monthly chain-linked EA indices per individual retailer we calculate an individual index per elementary aggregate with weighted arithmetic mean. Weights of retailers represent the market share (turnover) of individual retailer per individual EA. From individual indices we calculate weighted arithmetic mean aggregate indices, i.e. indices of groups (by ECOICOP) and the total price index.

The aggregation method for web-scraped items is very similar to the one used for scanner data. The biggest difference is that items are replaced with homogenous groups.

18.5.3. Chaining, linking and splicing methods

At aggregated level annual chain-link method is used where December of the previous year is the linking month.

In 2001 the indices were chain linked through the new index base, i.e. 2000 (2000 average = 100), and a new method of calculation was introduced. In 2006 indices have been linked through a new index reference period 2005 (average 2005 = 100). Since 2016 indices were linked through the new index reference period year 2015 (average 2015 = 100).

The splicing in the time series is not used.

18.5.4. Quality adjustment – Detailed information

Explicit methods: Direct price comparison is used for clothing and footwear, books (the list of most-read books is changed every month since we monitor the major publishing house in the country, which publishes monthly the list of most sold, i.e. popular, books - Top 10 for adults and children/youth). DVDs and computer games are replaced on a monthly basis with more popular ones - direct comparison is used. As regards new cars, mixed/combined approaches are used; in the case of significant change, quality adjustment is made (mostly option pricing complemented with supported judgmental methods). For quantity adjustment, package size adjustment is used (e.g. medicaments). Option pricing is the most commonly used explicit method (half of the price difference between the two models is attributed to the difference in quality). Sometimes, when other methods can't be applied, we change the base price of a replaced model with the replacement's base price (only if the December price of the replacement is known).

Implicit methods: The choice of a method also depends on the data available: overlap method for audio-video, photo equipment and the like (if data on prices in two consecutive periods are available). The bridged overlap method is applied in most cases when quality changes are detected. It’s applied for technical products, household appliances, audio-video goods and in a case of significant change in quality when no other useful information is available.

In 2022, the percentage of quality adjustments (ECOICOP 03-12) was 0.2%.

Some measures have been taken in accordance whit the recommendations on the bridged overlap method for situations such as the last price of the replaced (old) product-offer is a reduced price, the first price of the new product-offer is a reduced price, the first price of the new product-offer is unusually high and the matched sample of product-offers includes reduced or atypical prices, or shows a downward price trend during the product life cycle. The choice of method depends on the situation. Wherever possible (including bridged overlap) regular prices enter the bridge.

If this is not possible, the direct comparison method or the option pricing method is used. We also have the option to adjust the number of items that enter the bridge by excluding product-offers with unusual price changes or to use a typical price of such a product to calculate the quality adjustment. Still, we haven't used this so far.

18.5.5. Seasonal items

A Seasonal weights method is applied.

Product groups treated as seasonal are Fruit, Vegetables, Clothing, Footwear, Household appliances, Sports equipment, Recreational services and Package holidays.

For all the categories of seasonal items indices are calculated according to the Seasonal weights method (seasonal weighting limited to individual classes). Weights of predefined seasonal products during their non-season are distributed to other products within the same class. During the year class weights remain the same while the product’s annual average weight is the same as its base weight.

Not applicable.

None.