What does the survey comprise?
The monthly publication of changes in prices of consumer goods and services. The price changes are shown as an index. Inflation is calculated as the percentage of change of the consumer price index compared with the same month in the previous year.
Consumer goods and services purchased by households in the Netherlands.
Consumer goods and services.
Date/year survey started
The figures in the most recent month are provisional. They become definite when the figure for the subsequent month is published.
How is the survey conducted?
The study is based on monthly price observations at companies and organisations that supply goods and services to consumers.
Although many prices are observed by interviewers in retail outlets, more and more retail chains also provide price-data sets (scanner data). Statistics Netherlands also uses written and telephone surveys, internet monitoring, external registrations and brochure/catalogue information.
Companies, institutions, associations and government.
Over 1,300 items and services, and 10,000 respondents (excluding scanner data).
Statistics Netherlands checks the completeness and plausibility of the incoming data. If the data are incomplete or implausible the respondent is asked to provide more information. In the case of non-response, the data will be imputed (the necessary information is estimated based on the remaining observations). When a product or service in the survey package is changed, a correction is applied for any differences in quality between the old and the new version of the product.
To measure price changes, a package of goods and services is compiled. Each product or service in this package is assigned a weight, an indication of how important it is in the consumption pattern of Dutch consumers. The consumption expenditure of National Accounts is used to determine the weights of the various goods and services in the CPI. In addition, budget surveys and other external sources are also used. The weights of the products and services in the CPI are updated and published annually in January.
Quality of the results
The accuracy and representativeness of the CPI are guaranteed by measuring prices of a very large and diverse number of products. Each month the prices are measured at different sales channels throughout the country. However, it is impossible to calculate the degree of accuracy. The accuracy of price changes for a group of products is generally lower than that for the total consumption package. The survey response rate is over 95 percent.
Inaccuracies can arise at several stages in the production process:
• sampling respondents
• selection of representative items and estimation of quality differences
• measurement errors
• determination of weighting factors
• as a result of non-response
Where possible prices are included of products observed for the same respondent in two consecutive months. Since 2007 (series 2005=100), the weights are adjusted annually. At that moment a new package of products and services is determined for which prices are measured. The weights in the package are also updated. The data are therefore not the same year after year, but they are comparable.
The 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 another department.
In January 2010, Statistics Netherlands introduced a new method for computing price indexes in the CPI and HICP, based on scanner data. More information can be found in the survey description:
The use of supermarket scanner data in the Dutch CPI.