Consumer price indices (CPIs) measure changes over time in the level of prices of goods and services that households consume. In many countries, they were originally introduced to provide a measure of the changes in the living costs faced by workers, so that wage increases could be related to the changing levels of prices. However, over the years, CPIs have widened their scope. Nowadays, they are widely used as a macroeconomic indicator of inflation, a key statistic for governments and central banks for inflation targeting and for monitoring price stability. They are also used as deflators in national accounts. With the globalisation of trade and production and the liberalisation of markets, national governments, central banks and international organisations place great importance on the quality and accuracy of national CPIs, and in their international comparability.