Consumer price index (CPI) 2025=100
What does the survey entail?
Purpose
The monthly publication of price changes in consumer goods and services. The price changes are shown in the form of a price index. The annual rate of change is calculated as the percentage change of the CPI in a particular month compared to the same month in the previous year. This annual rate of change is known as inflation. The derived consumer price index is also calculated using this data. The derived index removes the effect of changes in the tax rates of certain products (e.g. VAT and excise duty on alcohol and tobacco) and the effect of subsidies and consumption-related taxes. It answers the question: how would prices have changed if the tax rates had remained the same?
Target population
Consumer goods and services purchased by households in the Netherlands.
Statistical unit
Consumer goods and services.
First year of survey
1938
Frequency
Monthly
Publication strategy
The figures of the flash estimate and the first publication of the indices are provisional. They become final when the figures for the subsequent month are published.
How is the survey conducted?
Type of survey
The survey is based on monthly price data collected from businesses and institutions that supply goods and services to consumers.
Data collection method
CBS increasingly uses transaction data (such as scanner data from supermarkets and other retail chains) and register data to monitor prices for the CPI. Web scrapers and automated online applications that collect prices automatically are also used. In addition, CBS conducts online surveys and prices are also monitored manually online.
Sources and respondents
In order to collect data on prices for the CPI, CBS consults businesses, institutions, associations and government bodies. CBS mainly receives aggregated source data that does not contain personal data. However, CBS does consult sources containing linked personal data for a number of price measurements:
- Online surveys can be sent to sole proprietorships, for example lawyers or painters;
- For rents, the Basisregistratie Kadaster (BRK) and the Eigendomsverhouding vastgoed (koop-huur) of the Netherlands’ Cadastre are used as source data. In addition, the Inkomensafhankelijke huurverhoging of the Tax Administration of the Netherlands is used. For the energy labels and energy indices of homes, data is obtained from the Netherlands Enterprise Agency (RVO);
- The Childcare benefit (Kinderopvangtoeslag - WKO) of The Tax Administration is used to measure price changes in childcare services.
- Data from the Central Administration Office (CAK) regarding care - for which users are required to pay a personal contribution - is used to measure price changes in nursing homes and domiciliary care.
Scope of sample survey
Every month, CBS collects data on prices from datasets including transaction prices and register data. In addition, with the help of automated online applications, web scrapers, online surveys and manual data collection via the internet, approximately 7,000 prices for around 650 different goods and services are recorded, with around 2,500 respondents.
Checking and correction methods
Once the data is received, CBS checks it for completeness and plausibility. If data is incomplete or incorrect, the respondent is asked to provide additional information. If no response is forthcoming, the relevant data is imputed (the necessary information is estimated on the basis of other data collected). If a clearly defined product undergoes changes, differences in the quality of the old and the new versions of the product can be taken into account.
Weighting
A package of goods and services is created in order to measure price changes. Each product or service in this package is assigned a weighting that indicates how important the product or service is in the consumption pattern of Dutch households. Data on consumer spending from the national accounts is used to determine the weighting of the various goods and services in the CPI. In addition, budget surveys and other external sources are used. The weightings for the product groups in the CPI are adjusted and published annually in January.
Quality of the results
Accuracy
Monitoring the prices of a very broad and diverse range of products on a monthly basis in different sales channels throughout the country maximises the accuracy and representativeness of the CPI. However, it is impossible to calculate its degree of accuracy. The accuracy of price changes for a specific product category is generally lower than for the total consumption package. Inaccuracies may arise at various points in the production process:
- when sampling respondents
- when selecting the representative items and estimating differences in quality
- when monitoring prices
- when determining the weighting factors
- as a result of non-response.
Comparability over time
Price changes are measured by including the prices of a broad range of products that have been surveyed over two consecutive months at the same retail outlet. The reference base is adjusted annually in January. At that moment, a new package of products and services is introduced, and the weightings are also updated. The data are therefore not the same year on year, but are comparable.
Quality strategy
The data is checked for internal consistencies and completeness. Wherever necessary, action is taken to verify the data. If the data is correct, the price indices are calculated and the results are verified and validated. The results are validated by other staff members than those who compile the figures. If it is found that incorrect data has been used to compile the price indices, there is a protocol to decide whether the results need to be revised. If the results are not revised, the price index will be brought to the correct level the subsequent month.