Basis 2004=100

Consumer price index basis 2004=100

To keep the index representative, its basket and calculation methods need to be reviewed on a regular basis. The eighth update since the creation of the index in 1920 was ended in 2005. January 2006 saw the publication of an entirely renewed consumer price index with base year 2004.
A complete renewal of the consumer price index is organised every eight years. Since January 2008 it is also updated every two years. In doing so, new products emerging in the consumption pattern of households can be added to the index basket and obsolete products can be removed. This will help the product basket to remain representative for the total duration of the index.

The product basket is divided into 12 groups according to the European COICOP classification (classification of individual consumption by purpose). The overview of the product basket also lists the corresponding weights.
The product basket and its weights were completely revised in the light of the household budget survey covering the 2004 calendar year. The basket with base year 2004 contains 507 goods and services (the representative items or so-called ‘witnesses’), compared to 481 in the old basket (base year 1996). 129 new witnesses were added and 103 obsolete witnesses were deleted. Additionally, 40 witnesses underwent a definition change. In 2008 the basket was extended to 518 representative items.

The 65 municipalities or localities where the prices were registered remained unchanged. The weights of these commercial centres were updated based on the population figures on 1 January 2004.

This downloadable table (XLS, 1.31 MB) illustrates the evolution of the consumer price index up to product level from January 2006 onward. The reference period of the figures is 2004 = 100.

The consumer price index is divided into 12 main groups. Each main group consists of a number of subgroups with according representative items.
The file contains the index evolution up to the lowest level of detail; the level of the 518 representative items in the index basket.

The relative weights (pro mille) of the products and groups are also included in the table.
These weights are based on the household budget survey and are in correlation with the consumer’s pattern of expenditure.

Until 2006 the product basket was only adjusted each time an index reform was carried out. The most recent index reforms were held in 1981, 1988, 1996 and 2004. Leaving the product basket unchanged for such long periods of time resulted in an index that gradually became less representative as it got older. To set this straight, the Index Commission decided during the most recent index reform of 2004 to update the product basket from then on every two years. This would remove products that have become less representative from the basket and replace them with new products if they have a substantial share in the pattern of expenditure. The update guarantees the representativeness of the consumer price index as an indicator of inflation during its entire course. If required, the updates are also used to correct calculation methods of goods and services.

The consumer price index remains a fixed-base Laspeyres index, which means that the weights of all main groups and sub-groups are fixed during its 8-year course. The new representative items are introduced with a weighting from one or more products within a group. Changing representative items or weights in the product basket does not distort the index.