What does the survey comprise?
PurposeThe monthly publication of price changes in consumer goods and services. Price developments are presented as index numbers. The annual rate of change of the HICP is an important indicator of inflation. The annual rate of change is calculated as the percentage change of the consumer price index (CPI) in a particular month compared to the same month in the previous year.Statistics Netherlands (CBS) also calculates the derived CPI. In this series, the effect of changes in the rates of product-related taxes (e.g. VAT and excise duty on alcohol and tobacco) and subsidies is eliminated. The derived CPI answers the question: how would prices have changed, if tax rates had remained the same?
Target populationConsumer goods and services purchased by Dutch households.
Statistical unitConsumer goods and services.
Year the survey started1938
Publication strategyThe status of the figures referring to the most recent month is provisional and becomes final when the figures for the next month are published.
How is the survey conducted?
Type of surveyThe study is based on monthly price observations among companies and institutions supplying goods and services to consumers.
Observation methodStatistics Netherlands uses more and more transaction data (like scanner data of supermarkets and more retail chains) and register data. Also internet robots which automatically collect prices are used. Another part of the prices is noted by interviewers in stores. In addition, Statistics Netherlands uses digital surveys, and prices are observed via the internet.
RespondentsBusinesses, institutions, associations and the various government levels.
Sample sizeEvery month many data are collected from datasets with transaction prices, register data and by internet robots. Additionally, more than 15 thousand prices of more than 800 goods and services are collected at more than 4 thousand respondents.
Checking and correction methodsStatistics Netherlands checks the completeness and plausibility of incoming data. If data are incomplete or implausible, the respondent is requested to provide additional information. In the case of non-response, the data will be imputed (the necessary information is estimated on the basis of other observations). When products or services in the survey package are changed, a correction is made for any differences in quality between the old and the new version of the product.
WeightingTo measure price changes, a package of goods and services is compiled. A specific weight, i.e. an indication of how important a product or service is in the consumption pattern of Dutch consumers, is assigned to all products and services in the package. Consumer spending data by National Accounts are used to determine the weights of the various goods and services in the CPI. In addition, budget surveys and other external sources are used. The weights of the product groups in the CPI are adjusted and published annually in January.
Quality of the results
AccuracyAccuracy and representativeness of the CPI are safeguarded by measuring prices of a very large and diverse range of products. Each month, 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 for the total consumption package. The survey response rate exceeds 95 percent.
Inaccuracies may 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