Statistics Netherlands (CBS)

Government finance and consumer prices statistics department.

CBS

Henri Faasdreef 312    PO Box 24500
2492 JP The Hague     2490 HA The Hague
The Netherlands

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 HICP covers the entire economic territory of the country. The Dutch Antilles and the small part of the Netherlands known as the ‘Belgian enclave’ are not covered. The islands of Bonaire, St. Eustatius and Saba are special municipalities of the Netherlands. For these islands separate CPI’s are calculated as of 2011. These are not included in the HICP.

3.8.1. Start of time series

The HICP series started in January 1997.

3.8.2. Start of time series - national specifics

The HICP of Statistics Netherlands is included in the index as of 1996.

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.

Statistics Netherlands sends preliminary data to Eurostat for the HICP Flash estimate in each month of the year. These data have not been published yet at the moment of sending. Apart from that there is no advance data sharing.

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.

All data that are more detailed than the statistical results that are regularly published are considered confidential. This includes prices, article weights, outlet weights and product descriptions. Confidentiality must ensure that CBS does not publish data on prices or sales volumes for individual enterprises or products. The confidentiality of product descriptions must also ensure that products included in the CPI or their prices can be used as a benchmark for product pricing decisions by companies.

Confidentiality of data is regulated by the 'Wet op het Centraal Bureau voor de Statistiek'. Also the EU General Data Protection Regulation is there for the protection of personal data.

HICP outcomes are published on an aggregated level only. All information furnished by data suppliers is treated confidentially. No data from individual data suppliers can be deduced from published data or press releases.

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.

Statistics Netherlands provides a schedule of CPI and HICP release dates well in advance (https://www.cbs.nl/en-gb/publication-calendar). In addition a weekly agenda, announcing press releases, is placed on the CBS website every Friday.

The release of the final HICP and HICP-CT data is always accompanied by a news release. At the same time, the detailed price index data are released on the publication database (StatLine). The figures are also available as open data in the form of datasets. By using web services, the most recent data can be retrieved, filtered and combined.

The HICP Flash estimate is published on StatLine at the same day as Eurostat releases the Flash estimate. The release of the HICP Flash estimate is accompanied by a news release and/or other (social) media exposure.

The press releases and detailed information are made public to all users at the same time. Press releases are announced well in advance via e.g. the publication calendar. There are no users that are granted special or pre-access to data.

Monthly

The HICP data are published together with the CPI data every month in a press release which also contains explanatory notes. Next to that the data is also published in an online database called StatLine and via open data resources. When the press has any questions, they can contact our spokesperson via the press office. Other users can obtain information via the information service.

The HICP flash estimate is also published together with the CPI flash estimate, monthly in a press release and on StatLine. This dissemination is limited to the figures of the all items level and a selection of special aggregates. 

All levels are published according to ECOICOP. The index figures are published with 2 decimals. The monthly and annual rate of change is published with 1 decimal. The figures and press releases are both disseminated in Dutch and in English.

Further methodology can be found at:

Brief survey descriptions

Additional descriptions cpi

Yearly base shifts (in Dutch)

The CPI/HICP press release is published on a monthly basis. The press releases start with a short analysis of current outcomes and developments. The Dutch version contains links to tables with time series for the overall CPI series, outcomes on a disaggregated level and international HICP figures. The releases also contain data on the contributions of disaggregated levels to the overall CPI. Apart from the press release the results are also published in the statistical bulletin, a monthly publication of Statistics Netherlands.

The release of the HICP Flash estimate is also accompanied by a press release and/or other social media exposure.

The Dutch HICP is published in several national publications. Publications are disseminated on the website of Statistics Netherlands and also in the statistical bulletin and StatLine.

The Dutch Central Bank and the CPB Netherlands Bureau of Economic Policy Analysis include the HICP in their forecasts.

Detailed HICP time series are available on the HICP database as well as on the database of Statistics Netherlands.

Detailed information about the HICP and HICP -CT can be found via HICP 2015 = 100

Detailed information about the contributions and impact on HICP and HICP -CT can be found via HICP 2015 = 100, detailed contributions and impact to the headline figure

Generally speaking micro data is not available for the general public. However, in exceptional cases anonymised micro data can be accessed by admitted third parties on request by using remote access. Detailed transaction data cannot be shared with third parties.

The HICP is disseminated on Eurostat's HICP website.

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 Dutch methodological notes on the HICP are published at www.cbs.nl.

• More information about the yearly base shift (in Dutch)
• Methodological report on consumer prices (in Dutch)
• Harmonized consumer price index 2015=100
• Calculation of contributions and impacts
• The impact of the corona crisis on compiling the CPI
• The consequences of  the corona crisis for the weight scheme (in Dutch)

There are no publicly available quality related documents.

Statistics Netherlands is certified according to ISO 9001 standards. The certification confirms that Statistics Netherlands fulfills the quality requirements for statistics production.

Also Statistics Netherlands follows the European statistics code of practice.

European statistics code of practice

11.1.1. Quality management - Compliance Monitoring

Compliance Monitoring

11.1.2. Quality assurance - national specifics

Statistics Netherlands is certified according to ISO 9001. In practical terms for the HICP, this means:

• all activities are documented
• documents, software and data files are well-structured and in order
• checks are carried out in critical process steps
• continuous improvement is integrated as a routine in the daily work: internal quality revisions assures the compliance to the ISO-standards
• issues are documented using the PDCA-method (plan, do, check, act).

A separate team of people checks the figures and after that the results are checked by an independent person who is not directly involved in the production of HICP.

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).

11.2.2. Quality assessment - national specifics

The quality of the HICP can be assumed to be very high. Its concepts and methodology have been developed according to international standards and using consumer price statistics experience from all EU Member States. HICPs are considered to be sufficiently accurate for all practical purposes they are put into. In particular it is the best measure of inflation for the euro area and European Union as a whole as well as for the comparisons of inflation across countries for which it is compiled. The indices are disseminated around the first week of the month following a predetermined timetable.

Further work is ongoing to improve the quality and in particular the comparability of the index. Key priorities are the treatment of owner-occupied housing (currently excluded) and greater harmonisation of methods for quality adjustment and sampling.

The HICP in the Netherlands is subject to an internal audit once every 3 years. There is a yearly ISO 9001 audit for the whole department.

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

The HICP/CPI figures are mostly used for:

• Wage indexations (by e.g. private companies),
• Pension indexations (pension funds),
• Rent indexations (landlords),
• Inflation monitoring (Central bank),
• Research (planning agencies and universities).

There is no user satisfaction survey available. The most important users of HICP data are represented in the so-called Macroeconomic Advisory Board (Adviesraad Macro economische statistieken). This board meets on a yearly basis to give their views on HICP related topics.

All ECOICOP indices at 5-digit level are disseminated above the weight limit of 1/1000.

The accuracy of HICP is generally considered to be high. 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 (National Accounts data, Household Budget Survey data, etc.) and prices (webscraping, scanner data, registrations, online surveys and central collection via the internet are used). The type of survey and the price collection methods ensure sufficient coverage and timeliness. The outlets, from which prices are collected, are chosen to represent the existing trade and services network and they are based usually on three main criteria: popularity with consumers; significant turnover from consumer sales; and availability of goods and services included in the HICP basket. All the private households in the economic territory of the country are covered, whether resident or not and irrespective of their income.

Furthermore, Eurostat and the Member States are actively following up an Action Plan concerning quality adjustment and sampling issues. Concrete best practices have been agreed for a range of specific goods and services (in particular cars, consumer durables, books and CDs, clothing and computers).

The sampling errors are reduced by using a sample of consumer prices that is as large as possible, given resource constraints.

For the HICP non-sampling errors are not quantified. They are reduced through continuous methodological improvements and survey process improvements, which can help avoiding coding and typing errors.

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 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 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. In January 2011 there is a break in the series due to new methods to compile price indices for package holidays and airline tickets. Also in April 2018 a level adjustment for clothing was carried out.

Differences between CPI and HICP

CPI and HICP are different in certain aspects. This section will in short summarize the differences. They can be subdivided into four themes:

• Target population; which consumers and which transactions are included in the index,
• Coverage; which consumption expenditures are included,
• Price definition; how are some prices defined,
• Classification.

Target population

This theme covers two subjects:

• The CPI uses a national concept, whereas the HICP uses a domestic concept,
• Consumption by institutional households.

The national concept of the CPI implies that all expenditures of consumers living in the Netherlands are included, regardless of whether these expenditures are in the Netherlands or abroad.

The domestic concept of the HICP implies that expenditures abroad of consumers living in the Netherlands are excluded from the HICP, but that expenditures of foreign visitors on Dutch territory are included.

Expenditures by people living in institutional households are included in the HICP. In the 2006=100 series these expenditures were excluded from the CPI. Starting from the 2015=100 series expenditures by people living in institutional households are included in the CPI excluding the own contributions that these people pay for living in the institution.

Coverage

Three groups of goods and services are included in the CPI but excluded from the HICP:

• Imputed rentals for housing,
• Contributions,
• Consumption related taxes.

For households renting a house, the rents payments are included in CPI and HICP. For households living in a house of their own imputed rentals for housing is included in the CPI and the developments of imputed rentals contribute to the CPI results. Owner occupied housing expenditures are excluded from the HICP.

The HICP does not consider subscriptions or contributions for recreational and sports clubs, labour unions and other NPISHs to be consumption expenditures but to be transfers. Also consumption related taxes are out of the scope of the HICP. Government services are included. On the other hand, own contributions paid for living in an institutional household are included in the HICP, but excluded from the CPI.

Price definition

For some product categories price definitions in HICP and CPI differ. There are differences in the treatment of parents’ contributions for child care. In the CPI the gross price for child care is observed. As a consequence the weight for child care is high. In the HICP only the parents’ own contributions are included. Contributions that the government pays to the parents are deducted from the gross price. Therefore also the weights for child care are lower. Finally changes in own contributions for health care that is covered in the base health insurance are treated differently. If a certain element of health care is taken out of the coverage of the base policy and the consumer has to pay for that care himself, this is reflected in the CPI only by an increase of the weight for health care. Likewise a change whereby previously uninsured health care is taken up in the base policy also does not lead to a decrease of the CPI.

In the HICP changes in the basic insurance policy are treated as price changes. A change whereby insured health care from a certain point in time is no longer covered by basic health insurance and for which the consumer must pay an own contribution is treated as a price increase from zero to the new own contribution or market price. Alternatively a change whereby a part of health care that was not insured is brought under the coverage of the basic health insurance is treated in the HICP as a price decrease from the existing price or own contribution to zero.

Classification

Differences in classification all have to do with product groups that are out of the scope of one of the two series.

 Included in the CPI, but not included in the HICP are:

• ECOICOP 042100 Imputed rentals for housing,
• ECOICOP 094130 Membership sports and recreation clubs,
• ECOICOP 130000 Consumption related taxes,
• ECOICOP 140000 Consumption abroad.

Included in the HICP, but not in the CPI are:

• ECOICOP 124020 Retirement homes for elderly persons and residences for disabled persons.

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

When errors are discovered or if new information leads to new results that have significant impact especially on the level of headline inflation, then all HICP's concerned are revised.

Revision of CPI and HICP figures takes place in the following cases:
1. If the impact on the annual rate of change of the CPI or HICP is 0.1 percentage points or more;
2. If the HICP takes figures from other, independent statistics, the HICP follows in principle the revision of these statistics. Examples of this are the rents and fuel prices;
3. Weights will not be revised if new data from the National Accounts become available.

The following additional comments can be made here:

• It does not matter for the review whether the published figures are provisional or final.
• The 0.1 percentage point impact counts as an absolute value for unrounded figures.
• If the CPI is revised, the HICP is also revised, and vice versa.
• Figures with a generally known, fixed starting date (such as tuition, public transport, municipal taxes) are not corrected (revised) with retrospective information, but are brought to the correct level when the new information arrives, unless the impact is 0.1 percentage points or more. In case the concerned figures are still flagged as provisional, they can also be brought to the correct level if the impact is below 0.1 percentage points.

Index numbers may be revised in the case of errors or when improved information leads to a significant change. A base-year revision does not lead to the backward revision of results. Statistics Netherlands has revised our HICP in the past 10 years.

The most important revision is the implementation of a new method for package holidays and passenger transport by air. The HICP headline inflation was affected (by between 0,1 and 0,3 percentage points) as well as the all items index and indices for passenger transport by air and package holidays for the months in the year 2011. The revisions for package holidays improved the accuracy of our HICP because in the new method real transaction prices are used versus list prices in the former method. The timing of the price changes according to Commission regulations was obviously also an improvement. Together with the revision a level adjustment was carried out by January 2011.

Also in April 2018 a level adjustment for clothing was carried out. For all details concerning this adjustment, see our publication.

Next to these revisions there is yearly a small revision of the HICP in July due to incomplete data for the rents at the moment of first publication. The first publication of the HICP of July is always flagged as provisional for this reason. The revision is usually small, since 2016 the difference between the provisional and the final publication has not exceeded an 0.1 index point on the ECOICOP level for CP041 - Actual rentals for housing.

Furthermore, the first publication of the HICP in January is always flagged as provisional, because in January there is increased chance that not all source data is available at the moment of the first publication. If new data becomes available afterwards, the January figures can then still be revised. This was done in 2023 for categories CP0442 - Refuse collection and CP0443 - Sewerage collection. This revision had an impact below 0.1 percentage points on the all items level.

18.1.1. Weights

The basis for determining the expenditure shares in 2022 is formed by the provisional consumption figures of the 2021 National Accounts. The amounts from the National Accounts are classified differently than in the HICP. The amounts according to this NA classification are distributed according to the classification of HICP article groups (ECOICOP groups) using a scheme.

The weights used in 2023 tries to approximate consumer spending in 2022. Significant changes in expenditure shares between 2021 and 2022 are updated in the amounts from the National Accounts for 2021. This is done in all categories. For the weights of the 2023 reporting year, the growth rate of the average of the first 3 quarters of 2022 compared to the first 3 quarters of 2021 has been added to the results.

Statistics Netherlands uses weights below the level of sub-index level for outlet types and articles. In addition and where possible, a weight is also allocated for the market share of the companies. The lowest level of aggregation is the level of outlet types and articles (7-digit). The source of these weights are obtained by scanner data and market research.

18.1.1.1. Compilation at elementary aggregate level

Statistics Netherlands uses weights below the level of sub-index level for outlet types and articles. In addition and where possible, a weight is also allocated for the market share of the companies. The lowest level of aggregation is the level of outlet types and articles (7-digit). For the outlets from which we receive transaction data, we use this data for outlet and product weights. For other outlets we use a combination of retail statistics and market research to determine weights. Most weights applied at the elementary aggregate level are updated yearly. There are no regional weights in the Dutch HICP.

18.1.1.2. Compilation of sub-index weights

The basis for determining the expenditure shares in 2022 is formed by the provisional consumption figures of the 2021 National Accounts. The amounts from the National Accounts are classified differently than in the HICP. The values according to this NA classification are distributed according to the classification of HICP article groups (ECOICOP groups) using a scheme.

The weights used in 2023 tries to approximate consumer spending in 2022. Significant changes in expenditure shares between 2021 and 2022 are updated in the amounts from the National Accounts for 2021. This is done in all categories. For the weights of the 2023 reporting year, the growth rate of the average of the first 3 quarters of 2022 compared to the first 3 quarters of 2021 has been added to the results.

For certain product groups, such as food, package holidays abroad, airline tickets and restaurants, additional data up to and including December 2022 have been used to better estimate the fourth quarter of 2022 and to check the results. Also turnover statistics up to October 2022 were used to check the figures.

The 4th quarter of 2022 is integrated by using the above-mentioned data. If no additional information was available, the growth rate of the first 3 quarters of 2022 compared to the first 3 quarters of 2021 was used instead to estimate the 4th quarter. When 4th quarter information was used, it replaced the growth rate of the first 3 quarters and the growth rate of 2022 compared by 2021 was added to the results.

18.1.1.3. Compilation of sub-index weights

The reference period is derived from National Accounts based on t-2 and updated to t-1.

18.1.1.4. Weights – plausibility checking

On various moments in the process of making the weighting scheme, the plausibility of the weights is checked. Data on household expenditure of the National Accounts (NA) department, which is used as input for the HICP weighting scheme, is compared to the same data that was provided in the previous year. The most notable absolute and relative changes are subsequently presented to experts of the NA department and have to be clarified by them. If the first version of the HICP weighting scheme is made, it is subjected to an extensive review. Members of the review committee consist of experts from within the HICP/CPI team, as well as experts from the NA department.

Throughout the year, commodity specialists of the HICP/CPI team make weighting matrices for the lowest level ECOICOP groups. These matrices indicate the relative weights on the level of item and outlet type for the coming calendar year and they are accompanied by a report that explains how both the choice of the items and the distribution of the weights have been established. In order to achieve that, the commodity specialists conduct market research, using data from different sources such as retail statistics, household budget surveys and trade associations. The weighting matrices as well as the report that goes with it, are reviewed by experts within the HICP/CPI team.

18.1.1.5. Price updating

Statistics Netherlands has applied price updating to make the expenditure shares representative for December t-1.

We do this according to the guidelines by dividing the December price index by the average price index of the past year. This factor is multiplied with the value of the NA-data.

The price update has been carried out at the level of the sub-index and outlet.

Statistics Netherlands has not applied price updating from year t-2 to year t-1 as 2022 expenditures were already taken into account.

18.1.1.6. Compilation of total household final monetary consumption expenditure

The basis for determining the Household Final Monetary Consumption Expenditure in 2022 is formed by the provisional figures of the 2021 National Accounts.

The growth rate of the average of the first 3 quarters of 2022 compared to the first 3 quarters of 2021 has been added to the results. To estimate the 4th quarter, other available, reliable, resources were used.

18.1.2. Prices

The price data is based on a mix of multiple data sources; survey data, administrative data sources, scanner data and webscraped data.

18.1.2.1. Data Source - overview  

The following sources are used for price data in the Dutch HICP:

• Survey data collected from online stores and by using questionnaires.
• Scanner data, data from stores with all transactions processed through the cash register.
• Data with average prices from market analysis companies.
• Web-scraping is used for collecting bulk data from websites.
• Administrative data source which contains information about prices and number of sold items.

18.1.2.2. Scanner data - general information

Statistics Netherlands processes scanner data for these types of retailers:

• Drugstores
• Consumer electronics
• Liquor stores
• Motorfuels
• DIY stores
• Supermarkets
• Department stores
• Travel agencies
• Internet shops
• Garden centers
• Shoe stores
• Clothing stores
• Household stores

18.1.2.3. Web scraping - general information

Web scraping is used to gather online price data from clothing and footwear retailers, furniture stores, hotels, wireless telephone services, bundled telecommunication services and selected airfares on a daily or weekly basis. The percentage of weight covered by web scraped data for clothing is 46% in men, 45% in women and 36% in children; 72% for other clothing articles; for footwear is 29% in men, 30% in women and 27% in children; 34% for household furniture; 8% for garden furniture; 42% for other furniture and furnishings; and 100% for hotels, wireless telephone services, bundled telecommunication services and international flights.

Web scraping is used both to represent e-commerce (online shopping) and as a proxy for physical shop price collection.

18.1.3. Sampling

18.1.3.1. Sampling design: locations for survey

Prices from all over the Netherlands are used for the observation. So, in the sampling design we include every region of the Netherlands (except the Caribbean part of the Netherlands).

18.1.3.2. Sampling design: outlets

The outlet selection is decided upon centrally. Outlets in the whole country are chosen for the survey. They are identified by the commodity specialists of our organization based on the Household Budget Survey and other market research.

Electronic questionnaires are sent to canteens, cafes, movers, funeral businesses, notaries, opticians, sport shops, flower shops and several other business types.

18.1.3.3. Sampling design: newly significant goods and services

Market analysts evaluate the market each year and update the basket of goods and services if considered appropriate. Identifying and including newly significant innovative products is part of this process.

In recent years, PVC floor coverings (2020), digital subscriptions for newspapers (2021), game apps, robot vacuum cleaners and coronavirus self-tests (2022) were introduced in the index.

Price data is collected every month.

18.3.1. Price collection surveys

Survey data is collected by electronic questionnaires and internal price collection.

18.3.2. Timing of price collection

Price collection in outlets is done in the first 3 weeks of the month.

The price data are checked for internal consistency and completeness. When necessary, action is taken to verify the data. If the data are correct, the price indices are calculated and the results are verified and validated. Validation is done by members of the team who are not directly involved in processing the price data, and therefore have an independent perspective.

18.4.1. Data validation - price data

The data is checked for internal consistency and completeness. Data entry errors are checked by the employee when the prices are entered into the computer. If the price differs from the previous price, the employee needs to fill in the reason for the differences. The consistency of the price information over time is monitored by following the same item for as long as being representative. Where necessary, additional price information will be noted so that this can be included next time. When observing an item, it must always remain within the framework of the price information that has been drawn up for the item. When extreme prices or price changes are observed, it is checked whether the price is correct and whether the price change can be explained. If necessary, this is corrected or the employee who noted the prices is alerted to this.

18.5.1. Elementary price index formulae

The HICP is compiled as a Laspeyres-type index. For most elementary aggregates a Dutot-index is compiled. In the case of transaction (scanner) data Statistics Netherlands uses mostly the QU-method. Price observations are not rounded but entered in cents. The HICP-weights (1/1000) are disseminated using two decimal places (smallest unit is 1/100000). All calculations are performed without any rounding in the calculation process. The index results are rounded to two decimal places at the point of publication. Annual rates and monthly rates of change are calculated from the published figures and then rounded to one decimal place for publication.

18.5.2. Aggregation of different data sources

We use Dutot for aggregation from representative to elementary aggregates. For most transaction data we use the QU method from GTIN to elementary aggregates. From there a Laspeyres-type index upwards.

18.5.3. Chaining, linking and splicing methods

Each December a new 'short' index series December Y=100 is started, using updated baskets and new weights. At each level of detail the January 'long series' index (published series) is calculated as Index (Jan; new short series)/100 * Index(December; long series). No splicing is made.

18.5.4. Quality adjustment – Detailed information

Hereby an overview of all the quality adjustment methods we are using:

• Direct comparison (e.g. clothing)
• Quantity adjustment (e.g. for tobacco)
• Option Prices (e.g. for cars)
• Supported Judgment (e.g. for electronics and boats)
• Overlap (not commonly used)
• 50% method (not commonly used)
• Targeted Mean imputation (not commonly used)

We cannot indicate per ECOICOP division as a percentage of all prices, how often a method was used. It is diverse and it does not depend on the ECOICOP but on the article.

Hedonic quality adjustment methods are not used.

The recommendations from 2021 on bridged overlap did not lead to changes for the Dutch HICP, as the listed situations were already avoided. Bridged overlap is not commonly used in the HICP of the Netherlands. Furthermore, the representativeness of the level of last prices of the replaced (old) product-offer and the first prices of the new product-offer are carefully considered when a disappearing product-offer is replaced with a new product-offer. If one or more of the four situations as described in the recommendations apply, the Netherlands would often use direct comparison or supported judgement. Depending on the type of product and the circumstances, other alternatives can also be used.

18.5.5. Seasonal items

In the Dutch HICP ECOICOPS for fish, fruit, vegetables, flowers, clothing, footwear and package holidays are considered seasonal products groups. For these aggregates a strict annual weights method is used. The weights of the in-season products are the same every in-season month.

Not applicable.

None.