The Consumer Price Index describes the price development of goods and services purchased in Finland by households resident in Finland. The Consumer Price Index is calculated with a method in which the prices of different commodities are weighed together with their shares of consumption. The calculation of the index follows Laspeyres’ price index formula whereby the shares of consumption used as the weights relate to the base period. The Consumer Price Index is used as a general measure of inflation. Consumer price indices that are reviewed at intervals of a fixed number of years are suitable for short-term examinations. The Cost-of-living Index 1952:10=100 is a long time series calculated from the latest Consumer Price Index (currently consumer price index 2005=100) and its development, therefore, follows the Consumer Price Index. Many rents, such as those on dwellings, business premises or land, are usually tied to the Cost-of-living Index. From the user’s point of view, the Cost-of-living Index is the most practical, because index revisions do not interrupt the series and the point figures of the Cost-of-living Index are published monthly at the same time as the Consumer Price Index. In addition to their national consumer price indices, the Member States of the European Union also produce the Harmonised Index of Consumer Prices (HICP), from which Eurostat, the Statistical Office of the European Communities, calculates the European Index of Consumer Prices and the Monetary Union Index of Consumer Prices. Calculation of the Harmonised Index of Consumer Prices is guided by EU Regulations. The main purpose for which the Harmonised Index of Consumer Prices is used is inflation comparison between the EU countries. The European Central Bank uses the Harmonised Index of Consumer Prices as the measure of inflation in its monetary policy. The Finnish Harmonised Index of Consumer Prices is mainly based on the same price data and national accounts data as the Finnish national Consumer Price Index. The development of the Harmonised Index of Consumer Prices, however, deviates from that of the national Consumer Price Index, because it includes fewer commodities. In the Harmonised Index of Consumer Prices consumption does not include owner-occupancy, lottery, betting and gambling, interest rates or fiscal charges. Its coverage of the national Consumer Price Index is therefore slightly less than 90 per cent. In addition, Harmonised Index of Consumer Prices at Constant Taxes (HICP-CT) is produced. The inflation measured by consumer price index consists mainly of products and services priced by enterprises and the public sector, and value added and commodity taxes. Some 25 per cent of the private consumption at a value of around EUR 61 billion described by the HICP consists of value added or other taxes. The index at constant taxes is based on the HICP so the two indices have the same weight structure and price data. The index at constant taxes is calculated with a method which holds the tax rate constant relative to the reference period. If there have been no changes in taxes, the indices show the same development. When tax changes take place, the impact of the tax change on commodity prices is eliminated from the index at constant taxes. The price impact of the tax changes is obtained by comparing the development of the HICP and HICP-CT.