Harmonised index of consumer prices (HICP) (prc_hicp)

National Reference Metadata in Euro SDMX Metadata Structure (ESMS)

Compiling agency: Statistics Poland (GUS)

Time Dimension: 2020-A0

Data Provider: PL1

Data Flow: HICP_NES_A


Eurostat metadata
Reference metadata
1. Contact
2. Metadata update
3. Statistical presentation
4. Unit of measure
5. Reference Period
6. Institutional Mandate
7. Confidentiality
8. Release policy
9. Frequency of dissemination
10. Accessibility and clarity
11. Quality management
12. Relevance
13. Accuracy
14. Timeliness and punctuality
15. Coherence and comparability
16. Cost and Burden
17. Data revision
18. Statistical processing
19. Comment
Related Metadata
Annexes (including footnotes)
 



For any question on data and metadata, please contact: EUROPEAN STATISTICAL DATA SUPPORT

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1. Contact Top
1.1. Contact organisation

Statistics Poland (GUS)

1.2. Contact organisation unit

Trade and Services Department

1.5. Contact mail address

Statistics Poland (GUS)
Trade and Services Department
Al. Niepodległości 208
PL - 00925 Warsaw
Poland


2. Metadata update Top
2.1. Metadata last certified 12/10/2020
2.2. Metadata last posted 12/10/2020
2.3. Metadata last update 12/10/2020


3. Statistical presentation Top
3.1. Data description

The harmonised index of consumer prices (HICP) is a consumer price index (CPI) that is calculated according to a common approach. It measures the change over time of the prices of consumer goods and services acquired by households. Because of the common methodology, the HICPs of the countries and European aggregates can be directly compared.

3.2. Classification system

European classification of individual consumption according to purpose (ECOICOP)

3.3. Coverage - sector

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

3.4. Statistical concepts and definitions

The main statistical variables are price indices.

3.5. Statistical unit

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

3.6. Statistical population

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

No deviations from the target population.

3.7. Reference area

3.7.1. Geographical coverage

The HICP refers to the economic territory of a Member State as defined by ESA2010.

3.7.2. Coverage error regions

The whole country is covered by NA, HBS and retail prices survey. There are also no regions excluded in the price collection procedure.

3.8. Coverage - Time

3.8.1. Start of time series

In accordance with Council Regulation (EC) No 1687/98, each Member State is required to produce a harmonised index of consumer prices (HICP) starting in January 1997.

3.8.2. Start of time series - national specifics

In Poland, the HICP was first compiled in 1999. The data for the period 1996-1998 is estimated. See the HICP database

3.9. Base period

2015=100


4. Unit of measure Top

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).


5. Reference Period Top

HICP is a monthly statistics.


6. Institutional Mandate Top
6.1. Institutional Mandate - legal acts and other agreements

Harmonised Indices of Consumer Prices (HICPs) are harmonised inflation figures required under the Treaty on the Functioning of the European Union. Council Regulation (EC) No 2016/792 of 11 May 2016 (OJ L 135) sets the legal basis for establishing a harmonised methodology for the compilation of the HICP, the MUICP and the EICP.
The Commission has brought forward detailed Regulations establishing the specific rules governing the production of harmonised indices.

Regulations:

  • Initial implementing measures (1749/1996)
  • Sub-indices (2214/1996)
  • Weights (2454/1997)-repealed
  • Coverage of goods and services (1687/1998)
  • Geographic and population coverage (1688/1998)
  • Treatment of tariffs (2646/1998)
  • Treatment of insurance (1617/1999)
  • Revised sub-indices (1749/1999)
  • Treatment of products in the health, education and social protection sectors (2166/1999)
  • Timing of entering purchaser prices (2601/2000)
  • Treatment of price reductions (2602/2000)
  • Treatment of service charges (1920/2001)
  • Minimum standards for revisions (1921/2001)
  • Common index reference period (1708/2005)
  • Temporal coverage of price collection (701/2006)
  • Sampling (1334/2007)
  • Seasonal products (330/2009)
  • Weights (1114/2010)
  • Owner-occupied housing (93/2013)
  • Common index reference period (2015/2010)

 

All relevant regulations as well as further methodological details can be found in the HICP section on Eurostat's website under Methodology => Legislation.

6.2. Institutional Mandate - data sharing

None.


7. Confidentiality Top
7.1. Confidentiality - policy

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

The Law on Public Statistics issued on 29 June 1995 with further amendments.

7.2. Confidentiality - data treatment

According to policy rules (see point 7.1).
Only aggregated results are published.


8. Release policy Top

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 Eurostat protocol on impartial access to Eurostat data for users.

8.1. Release calendar

The HICP release schedule is published at the end of each year for the full following year. It is publically available on Eurostat's website and a reference to this schedule is made on Statistics Poland website.

8.2. Release calendar access

A reference to Eurostat's website and the HICP Release schedule is made in the section of Statistics Poland website dedicated to HICP.

8.3. Release policy - user access

All users have equal access to HICP data which is available in Eurostat’s database. There is no national pre-access to the data. In addition HICP indices and rates of change for Poland (‘All-items’ main heading) are available on Statistics Poland website after its publication by Eurostat. When most up-to-date data is published in the table, the information of the new data availability appears in the News section of Statistics Poland website.


9. Frequency of dissemination Top

Monthly


10. Accessibility and clarity Top

The HICP data for Poland is published on Statistics Poland website after its publication by Eurostat. Forms of publications include: table with data, reference to HICP data in the CPI News Release, publication on prices. All the forms of publications are both in Polish and English. The data for Poland is published the same way as by Eurostat, i.e. with one decimal place.

10.1. Dissemination format - News release

The HICP data for Poland (All items) is published on Statistics Poland website (table with data) after its publication by Eurostat. Reference to HICP data is also made in the CPI News Release.

10.2. Dissemination format - Publications

HICPs for the 12 main ECOICOP divisions are presented in the yearly publication 'Prices in the National Economy'. 'Information on socio-economic situation of the country' contains the moving average and annual rates of change (monthly data) for the total HICP. 'Statistical Yearbook of the Republic of Poland' and 'Statistical Bulletin' hold the total HICPs.

10.3. Dissemination format - online database

HICP database: Eurostat’s website, Statistics Poland website.

10.4. Dissemination format - microdata access

None.

10.5. Dissemination format - other

None.

10.6. Documentation on methodology

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

The basic methodology for the Polish HICP is presented in the publication 'Prices in the national economy' and in 'Statistical Yearbook of the Republic of Poland'.

Additional information on methodology can be obtained on request from Statistics Poland Trade and Services Department.

10.7. Quality management - documentation

Compliance Monitoring Information notes available in the Eurostat's HICP site, under 'Methodology' => Compliance monitoring.


11. Quality management Top

Documentation on procedures applied for quality management is available on the Statistics Poland website:
https://bip.stat.gov.pl/en/activity-of-public-statistics/quality-in-statistics/

The legal basis of the quality policy of the Polish official statistics is the internal Regulation of the President of Statistics Poland (No 35 of 28th December 2011) on measurement, evaluation and monitoring of statistical surveys quality.
 
The applied quality policy is based on the following International and European standards:
• Fundamental Principles of Official Statistics
• European Statistics Code of Practice
• Quality Assurance Framework QAF
• Regulation (EC) No 223/2009 of the European Parliament and of the Council of 11 March 2009 on European statistics (amended on May 2015)

For measurement and assessment of the quality of statistical surveys, the following tools are applied:
•standard quality reports,
•standard quality indicators,
•self-assessment checklist,
•audits/peer reviews.

11.1. Quality assurance

11.1.1. Quality management - Compliance Monitoring

Compliance Monitoring

11.1.2. Quality assurance - national specifics

Controls on quality of the data

To counteract possible errors or mistakes, controls are implemented at different stages of the survey.

Price collectors are supervised and continuously controlled by the staff of the Regional Statistical Offices (RSOs). This also includes random checks of prices and products at outlets on a day after regular price collection. A controller checks whether the product observed is available on the outlet shelf and if its quality is the same as described in the form, and also if its price was correctly registered by the price collector. 

There is a special software for the automatic control of codes, sale units and price range. If the discrepancy between the last month’s price and the current month’s price exceeds an indicated range, the software requires further checks to be carried out and comments are sent to the central office. Any replacements have to be commented upon and explained. Then the necessary additional information from all the RSOs is gathered by the central office and the Price Statistics Centre of the Regional Statistical Office in Opole responsible for the prices control at the country level. 

The final control is applied in the central office, which also takes into consideration prices of comparable products recorded elsewhere and suspected data are explained by the RSOs.

11.2. Quality management - assessment

11.2.1. Compliance monitoring - last report and main results

Compliance Monitoring

11.2.2. Quality assessment - national specifics

Quality reports prepared by Statistics Poland are adapted to ESS standards, they are statements concerning the quality of data, containing the description of the basic components of quality: relevance, accuracy, timeliness and punctuality, accessibility and clarity, comparability and coherence, as well as the amount of survey costs and the burden on respondents, confidentiality, transparency and data security.
Analysis of the quality of each component includes: the description of the component, the measurement of quality, proposals to improve the quality of a given component. Furthermore, the summary report indicates the scope of  components, in which it is possible to improve the quality and reduce the cost of the survey and contains an analysis of linkages between the individual components:

  • Timeliness and accuracy of data,
  • Accuracy and usefulness of data,
  • Usefulness and timeliness of data,
  • Comparability and usefulness of the data,
  • Temporal and spatial comparability

To measure the quality of the individual components, quality measures are used. Quality reports both in the extended and a simplified version are universal in nature and apply to both full and representational surveys, company surveys, as well as household surveys, surveys based on administrative sources, census surveys or  surveys based on different sources of information, as the system of national accounts.
When analysing the survey in the context of the quality aspects, very helpful are also the recommendations on the quality, provided by the European Commission within the thematic regulations concerning individual statistical surveys.


12. Relevance Top
12.1. Relevance - User Needs

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

Government, self-government administration, Central Bank, researchers

12.2. Relevance - User Satisfaction

Not available.

12.3. Completeness

All requested ECOICOP indices and weights down to the 5-digit level are produced.


13. Accuracy Top
13.1. Accuracy - overall

The accuracy of HICP is generally considered to be high. Any unusual price movements are investigated at all stages of compilation. From the regional price collectors to the central office.

13.2. Sampling error

Statistics Poland tries to reduce the sampling errors by using a sample of consumer prices that is as large as possible.

13.3. Non-sampling error

Statistics Poland tries to reduce non-sampling errors through continuous methodological improvements and survey process improvements such as computer assisted price collection, which can help avoiding coding and typing errors.


14. Timeliness and punctuality Top
14.1. Timeliness

The full set of HICPs is published each month according to a pre-announced schedule, usually between 15 and 18 days after the end of the reference month. Each year, the January news release is published at the end of February to allow for the annual update of the weights 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.

14.2. Punctuality

Since the March 1997, launch of the HICP release, the HICP for the country groups aggregates has always been published on the pre-announced release dates.


15. Coherence and comparability Top
15.1. Comparability - geographical

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

To this end, definitions and classifications have been harmonised in a series of legal acts. The HICP is produced according to these minimum standards that may be applied with some flexibility as long as 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 from an index compiled following the minimum standards (Article 4 of Council and Parliament Regulation (EU) 2016/792).

15.2. Comparability - over time

HICP data are comparable over time. There have been several improvements in methodology since HICP was introduced with the aim of improving reliability and comparability of the HICP. These changes may have introduced breaks in time series. However, back calculations under the newer standards were performed when appropriate basic data was available.

15.3. Coherence - cross domain

Differences between the HICP and national CPI
The expenditure of institutional households and consumption expenditure of non-residents in the economic territory of the country is included in the HICP but excluded from the national CPI.
The consumption expenditure on games of chance is included in the national CPI but excluded from the HICP.
Due to the different coverage of consumption expenditure, the weights used for the HICP and CPI differ.
The main source of HICP weights are National Accounts while the system of weight for CPI is based on data from Household Budget Survey. The National Accounts reference period for weights is the year t-2 (weights are price-updated to December t-1) while the household budget survey data derive from the year t-1.

15.4. Coherence - internal

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


16. Cost and Burden Top

Not available


17. Data revision Top
17.1. Data revision - policy

The HICP series, including back data, is revisable at any point in time under the terms set in Commission Regulation (EC) No 1921/2001 of 28 September 2001. The published HICP data may be revised for corrections, and new or improved information.

17.1.1. Data revision - policy - national specifics

The HICP series, including back data, is revisable at any point in time under the terms set in Commission Implementing Regulation (EU) 2020/1148 of 31 July 2020. The published HICP data may be revised for corrections, and new or improved information.

CPI is not revisable (the exception is data for January due to revision of weights).

17.2. Data revision - practice

The HICP compiled by Statistics Poland is subject to revision, when e.g. there are major changes in coverage or the methodology implemented. The data is also revised if mistakes are detected.

There were two cases of revision over the last 10 years:

  • For January 2014: in connection with the introduction of the ECOICOP classification to the calculation of HICP indices since 2014 the weights and HICP indices for January 2014 were sent to Eurostat as preliminary data; after completing the software calculating the indicators according to the new classification, and after thorough examination and analysis, the revised data was again sent to Eurostat.
  • In 2017 because of the need to exclude public insurance connected with health (ECOICOP subclass 12.5.3.1).


18. Statistical processing Top
18.1. Source data

18.1.1. Weights

Weights are calculated using NA data (t-2) and are updated annually. Where necessary data obtained from NA is disaggregated into lower level based on HBS data. For the calculation of the index in a given year a weighting scheme is used covering 12 consecutive months from two years before, expressed in the prices from December of the previous year.

18.1.1.1. Compilation at elementary aggregate level

Weights are calculated using NA data (t-2) and are updated annually.  

18.1.1.2. Compilation of sub-index weights.

In some cases within ECOICOP subclasses, there is an additional national 6-digit level. Where necessary data obtained from NA is disaggregated into lower level based on the results of the Household Budget Survey.

18.1.1.3. Reference period higher levels

For each level of the HICP index the same reference period is applied. For the calculation of the index in a given year a weighting scheme is used covering 12 consecutive months from two years before, expressed in the prices from December of the previous year.

18.1.1.4. Weights - plausibility checking

Weights are updated annually using NA and HBS data. e.g. the direction of changes is compared.

18.1.2. Prices

Price data is based mainly on survey data sources. In addition, on transaction data obtained directly from data providers.

18.1.2.1. Data Source - overview  

Price data is based mainly on survey data sources. In addition, on transaction data obtained directly from data providers.

18.1.2.2. Scanner data - general information

Generally not applicable; however, during the covid pandemic months, scanner data is being used as an additional source for some food categories with high share of missing quotations.

18.1.2.3. Bulk web scraping - general information

Not applicable.

18.1.3. Sampling design and procedure

18.1.3.1. Sampling design: regions - general information

The whole country is covered by NA, HBS and retail prices survey.
In the price collection procedure there are no regions excluded. Prices are collected among 16 voivodeships. A voivodeship is the highest level of fundamental territorial division of the country (territorial self-government). For the purpose of the price survey, in each voivodeship there are price survey regions (their number depends on the size of the voivodeship). There are 207 price survey regions in total.

18.1.3.2. Sampling design: outlets - general information

Price quotations are conducted in retail outlets, in catering establishments and in entities providing services that fall within the price survey region. The outlets involved in the survey sample correspond to the most common shopping venues and reflect the diversity of a distributive network within the price survey region. The current survey arrangement does not provide for the application of weights when taking into consideration the shopping venues. The prices of consumer goods and services are quoted in approximately 170 retail outlets per region.

18.1.3.3. Sampling design: products - newly significant goods and services

The verification of items is performed once a year, while the replacements (change of a particular quoted product with specified quality parameters and manufacturer in the region of price survey) are done when the need occurs.
Identification of the newly significant goods and services is based on proposals from regional statistical offices, detailed HBS sourced data, available transaction data. While observing local markets, the price collectors gather information concerning changes in the assortment offered, sales structure, market sectors and significance.
New items are included in the price survey at the beginning of a new year. To achieve price dynamics in January in relation to the previous month, there is an additional quotation performed in December t-1. However, in the case when there is a necessity to change the product quoted so far at the retail outlet to another one, within the same description of the item, the changes occur on an ongoing basis. Completely new items are distinguished from the ones with the altered (updated) description concerning basic quality parameters

18.2. Frequency of data collection

Price data is collected every month.

18.3. Data collection

18.3.1. Price collection surveys

Survey data is collected mainly by price collectors. There are 207 price collectors on permanent basis. The price collectors also conduct other surveys not connected with prices, e.g. living conditions surveys and the LFS. In recent years, other methods of obtaining data have become more important. The share of items for which prices are collected centrally is increasing. Their share amounts to 21,5% of the sample.
The central collection of data related to price includes the following: uniform retail prices in the country, prices of selected goods and services purchased via the Internet, used cars, new cars (in addition to field collection), financial services provided by banks and electricity.
Transaction data obtained directly from their owners is also gradually implemented: motor vehicle insurance, health insurance (in addition to field collection), contents insurance (in addition to field collection), fuels for personal transport equipment.  
Within the survey of uniform retail prices in the country, the categories observed are, for example: pharmaceuticals (with reimbursement); sanatorium services; transportation services; postal services; telecommunications services; radio and TV payments; newspapers; magazines; administrative fees; legal and accounting services.
Within the survey of retail prices of goods and services purchased via the Internet, prices of items which reflect the most popular product groups purchased from online shops are quoted. Items belong for example to the following groups: food and non-alcoholic beverages (since 2017); men's clothing; women's clothing; children's clothing; men's footwear; furniture for apartments or houses; bedclothes; basic household appliances; motor tools and equipment; pharmaceuticals; therapeutic devices and equipment; spare parts and accessories for private means of transport; telecommunications equipment; equipment for receiving, recording, and playing sound; equipment for receiving, recording, and playing sound and images; phonographic and cinematographic equipment; equipment for processing information; recorded storage devices; durable-use equipment for indoor recreation; games, toys, and collectable goods; sports and camping equipment for outdoor recreation; goods for household pets; photography services; books; package holidays; accommodation services; other personal hygiene devices, goods and products; watches and clocks; goods for children.

18.3.2. Timing of price collection

The price recording period lasts from the 5th till the 22nd day of the reporting month (since 2011). Survey on fresh fruit and vegetables prices is conducted twice a month, between 5-13 and 14-22 day of a month.
Due to coronavirus crisis for some months the quotation period was modified to maintain the similar number of price quotations (to an extent possible).

18.4. Data validation

Verification of prices: collectors verify all price changes and are required to provide explanation for unusual movements. Special software is used for this purpose. Statisticians analyse every item index to ensure that price movements are consistent with external information, such as market observation results, trade statistics and producer price statistics.

Data validation: checks are made at all stages of index compilation – starting from price collectors up to the central office staff.
Price changes are subject to in-depth analysis, both at the regional and national level. Typical price dynamics are considered. In the case of a different trend (e.g. increased demand but a drop of prices in the case of seasonal articles in high season, and/or the presence of the opposite trend in certain region of price survey in comparison to other regions), such situation is explained and adjusted if possible. Similar explanations are applied to extreme price level values – analysis is focused primarily on quotations of the new or seasonal items in the first month of the new season.

18.4.1. Data validation - price data

Quotations of individual items are thoroughly analysed at various stages of index calculation. Price collectors use mobile devices with a special program that has been developed to compare the price of the  surveyed month with the price from the previous month. If the calculated price index exceeds the specified range, software requires a detailed check, carried out by the price collectors in the field. Should it be impossible to quote a particular item, the program enforces entering a special code to indicate the absence of quotations, the need to use the code in the absence of quotations indicates that the pollster did not forget about the quotation, and the particular product or service is simply not available in a given area. In the case where it is a temporary lack of quotations, the missing price is estimated at a later stage. If the recorded price is correct, i. e. it applies to the item comparable in quality to the previous month, the price collector selects the special code explaining the decrease or increase in the quoted prices. However, if the item is different in terms of quality than the one quoted in the previous month, this situation is also indicated in the program by the price collector, in order to, at a later stage of the analysis, make an adjustment for a change in quality. Then checks are carried out of the completeness and adequacy of the quoted items at the level of voivodeships. The missing information and outliers prices are explained. The next step is to analyse the quoted prices across the country. It is pursued by one of the regional statistical offices specializing in price surveys. At this stage, attention is also paid to the completeness, quality and accuracy of the quoted prices, missing prices and price outliers unconfirmed at an earlier stage.
The final check is carried out at the central office during the calculation of the index. At this stage, the prices of comparable products quoted in other regions are taken into account. Suspicious/uncertain data is examined again with the regional statistical offices.
In addition to the expert analysis of the developed indexes, the Department uses specially developed software in order to validate the calculated data.

18.5. Data compilation

18.5.1. Index formulae

Polish HICP is a Laspeyres-type index. Pursuant to legislation Jevons index, i.e. geometric average of the price relative of the month analysed and the previous one, is applied in order to calculate monthly price indices (the previous month = 100) for basic aggregates. Monthly indices with the base of December of the previous year for basic aggregates are calculated with the use of chain linking method with the application of indices with the previous month base. While preparing weights and indices data for publishing purposes, the highest possible accuracy is applied.

18.5.2. Aggregation method

The data basis and first stages of the calculations are the same for CPI and HICP.

• prices:
the prices are collected every month by price collectors in 207 survey regions, as well as centrally
• index from prices:
- in the case of the data collected by price collectors, the next step is to calculate an index for a particular item for each of the survey regions, i.e. unweighted price to price comparison (current month to previous month); next, the national index for a particular item is calculated, i.e. a geometric average of all indices from all survey regions,
- in the case of central collection, an index for a particular item is calculated, i.e. unweighted price to price comparison (current month to previous month);
• aggregation of items into elementary aggregates (m/m-1 indices):
the obtained price-to-price indices are then aggregated into the lowest levels of classification (ECOICOP 5-digit levels or lower 6-digit level); this is done with the use of the Jevons index (unweighted geometric mean of the price relatives – obtained in the previous stage, i.e. current month to previous month); we obtain the monthly price indices (the previous month = 100) for elementary aggregates


For the purpose of the HICP the next steps are:
• m/Dec t-1 indices for elementary aggregates
monthly indices with the base of December of the previous year for elementary aggregates are calculated with the use of chain linking method with the use of m/m-1 indices  
• m/Dec t-1 indices for higher levels of aggregation
The elementary indices (m/Dec t-1) are then aggregated upwards (ECOICOP classification) using fixed annual weights according to Laspeyres formula
• m/2015=100 for elementary and higher level categories
Monthly indices of the given year (2015 = 100) are calculated with the use of the chain linking method and the monthly indices (December of the previous year = 100).

18.5.3. Chaining and linking method

Chain linking method is applied at two stages of index calculation. To calculate monthly indices for elementary groups with the base of December of the previous year with the use of monthly indices (the previous month = 100) and to calculate one-based indices (2015 = 100) using monthly indices (December of the previous year = 100).

18.5.4. Quality adjustment

Replacement of an item takes place in the situation when the product being so far an item will not be sold any more or it will become less common/popular. The following corrections of quality are used:
•    direct comparison – when a new product is regarded to be equivalent to the previous one as far as the quality is concerned, which means that it comes from the same manufacturer, it has the same composition and technical and qualitative parameters significant for the purchaser, it has the same sales unit or there is a minor difference related to this matter, it has packaging of the same type, it is of the same kind, the differences are insignificant for the purchaser and may concern characteristics connected to consumer’s taste and preferences,
•    correction related to changes in packaging sizes – a method used in the case of changing the product weight by the manufacturer, the size of the packaging being the only significant change of quality,
•    overlap – permissible in the case of change of outlets, the old and the new one are observed at the same time (so called double-track quotation is performed),
•    bridge overlap – the only possibility to estimate the quality change is to acknowledge that the price change of the substitute item in a particular survey region is equivalent to the average price change of the items quoted in the other or selected (e.g. these where the quotations are performed in the retail outlets of the same type) price survey regions,
•    option costs – a method used when a new product’s quality is better in comparison with the previously observed one, i.e. it was enriched with an additional characteristic, and information on the price of this supplement is available and possible to estimate,
•    50% of the option – it is a special type of option costs method used for estimating prices of new cars,
•    expert method – used mainly during quotations of uniform prices in the country or goods purchased via the Internet.
 

Examples of applying quality adjustment methods:
•    correction related to changes in packaging sizes – e.g. food, chemicals,
•    option costs – e.g. computers, audio-visual, photographic, and IT equipment (difficult to apply, therefore it is seldom used),
•    50% of the option – cars,

Indirect methods of quality correction:
•    overlap – permissible in the case of change of quotation point,
•    bridge overlap – for a variety of products,
•    direct comparison – e.g. clothes and footwear, books, computer games (rapidly changing market), recorded storage devices.
B-type methods are most commonly applied.

18.5.5. Seasonal items - general information

Following the requirements specified in Commission Regulation No 330/2009, since 2011 Statistics Poland have modified methods of including seasonal products. Initially, the changes concerned only groups mentioned in the regulation (‘Fish’, ‘Fruit’, ‘Vegetables’, ’Clothes’ and ‘Footwear’), however, over the years new policy was applied to other seasonal items.

18.6. Adjustment

Not applicable.


19. Comment Top

Due to coronavirus pandemic since around the middle of March 2020 (closed shops, lack of provision of some services, inability to collect prices in the field), there was a different approach to data from March 2020.
For information on the compilation of the HICP during the COVID-19 crisis please see Eurostat HICP metadata.


Related metadata Top


Annexes Top